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  • 1.
    Abel, Martin
    et al.
    Department of Physics, University of Texas, Austin, TX 78712, United States.
    Frommhold, Lothar
    Department of Physics, University of Texas, Austin, TX 78712, United States.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg, SE 412 96 Gothenburg, Sweden.
    Collision-induced absorption at wavelengths near 5 μm by dense hydrogen gas2009In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, no 18, article id 181102Article in journal (Refereed)
  • 2.
    Antipov, Sergey V.
    et al.
    Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Nyman, Gunnar
    Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Spin-orbit and rotational couplings in radiative association of C(3P) and N(4S) atoms2011In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 135, no 18, article id 184302Article in journal (Refereed)
  • 3.
    Antipov, Sergey V.
    et al.
    Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Sjölander, Tobias
    Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden; University of Oxford, Oxford, United Kingdom.
    Nyman, Gunnar
    Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Rate coefficient of CN formation through radiative association: A theoretical study of quantum effects2009In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, no 7, article id 74302Article in journal (Refereed)
  • 4. Antzutkin, Oleg
    et al.
    Song, Zhiyang
    Stockholm University.
    Feng, Xiaolong
    Stockholm University.
    Levitt, Malcolm H.
    Stockholm University.
    Suppression of sidebands in magic-angle-spinning nuclear magnetic resonance: general principles and analytical solutions1994In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 100, no 1, p. 130-140Article in journal (Refereed)
    Abstract [en]

    Several theoretical and experimental aspects of sideband suppression in the nuclear magnetic resonance (NMR) spectra of rotating solids are considered. The principles of sideband suppression are explored using general symmetry arguments and previous treatments are examined critically. Analytical solutions are given for sideband suppression pulse sequences employing four, five, six, and nine pulses. The analytical solutions for four pulses are complete. Experimental demonstrations are given. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.

  • 5.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Tycko, Robert
    National Institutes of Health.
    High-order multiple quantum excitation in 13C nuclear magnetic resonance spectroscopy of organic solids1999In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 110, no 6, p. 2749-2752Article in journal (Refereed)
    Abstract [en]

    Excitation and detection of high-order multiple quantum (MQ) coherences among 13C nuclear spins in singly-13C-labeled organic solids is demonstrated experimentally. MQ signals involving at least ten quanta of spin angular momentum are observed in nuclear magnetic resonance (NMR) measurements on polycrystalline L-methionine-methyl-13C and L-alanine-1-13C, using a time-reversible multiple pulse excitation sequence modified specifically for experiments on systems with weak homonuclear dipole-dipole couplings and strong inhomogeneous interactions such as anisotropic chemical shifts. The feasibility of high-order MQ excitation and detection in 13C-labeled organic solids promises to expand significantly the range of applications of MQ NMR as a structural tool, to include such systems as 13C-labeled synthetic polymers and biopolymers.

  • 6. Arvantidis, J.
    et al.
    Meletov, K.P.
    Papagelis, K.
    Ves, S.
    Kourouklis, G. A.
    Soldatov, Alexander
    Prassides, K.
    Raman modes of the two-dimensional tetragonal polymeric phase of C60 under high pressure2001In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 114, no 20, p. 9099-9104Article in journal (Refereed)
    Abstract [en]

    The effect of high hydrostatic pressure, up to 12 GPa, on the phonon spectrum and the material stability of the two-dimensional (2D) tetragonal C60 polymer have been studied by means of Raman spectroscopy in the frequency range 100-2000 cm-1. A number of Raman modes appear in the spectrum for pressures above ~1.4 GPa, whose intensities increase with pressure. The pressure coefficients of the majority of the phonon modes change gradually to lower values for pressures around 4.0 GPa. The deformation of the C60 molecular cage along with the change of the material to a more isotropic state (as far as its elastic properties are concerned) resulting from the application of high pressure may be causing the observed effects in the Raman spectra. These effects are reversible upon pressure release and therefore the material is stable in the pressure region investigated.

  • 7.
    Avakyan, Leon
    et al.
    Department of Physics and I3N, University of Aveiro, Aveiro, Portugal.
    Paramonova, Ekaterina
    Institute of Mathematical Problems of Biology, Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, 142290 Moscow Region, Russian Federation.
    Coutinho, José
    Department of Physics and I3N, University of Aveiro, Aveiro, Portugal.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Bystrov, Vladimir
    Institute of Mathematical Problems of Biology, Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, 142290 Moscow Region, Russian Federation.
    Bugaev, Lusegen
    Physics Faculty, Southern Federal University, Rostov-on-Don 344090, Russian Federation.
    Optoelectronics and defect levels in hydroxyapatite by first-principles2018In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 148, no 15, article id 154706Article in journal (Refereed)
    Abstract [en]

    Hydroxyapatite (HAp) is an important component of mammal bones and teeth, being widely used in prosthetic implants. Despite the importance of HAp in medicine, several promising applications involving this material (e.g., in photo-catalysis) depend on how well we understand its fundamental properties. Among the ones that are either unknown or not known accurately, we have the electronic band structure and all that relates to it, including the bandgap width. We employ state-of-the-art methodologies, including density hybrid-functional theory and many-body perturbation theory within the dynamically screened single-particle Green's function approximation, to look at the optoelectronic properties of HAp. These methods are also applied to the calculation of defect levels. We find that the use of a mix of (semi-)local and exact exchange in the exchange-correlation functional brings a drastic improvement to the band structure. Important side effects include improvements in the description of dielectric and optical properties not only involving conduction band (excited) states but also the valence. We find that the highly dispersive conduction band bottom of HAp originates from anti-bonding σ* states along the ⋯OH-OH-⋯ infinite chain, suggesting the formation of a conductive 1D-ice phase. The choice of the exchange-correlation treatment to the calculation of defect levels was also investigated by using the OH-vacancy as a testing model. We find that donor and acceptor transitions obtained within semi-local density functional theory (DFT) differ from those of hybrid-DFT by almost 2 eV. Such a large discrepancy emphasizes the importance of using a high-quality description of the electron-electron interactions in the calculation of electronic and optical transitions of defects in HAp.

  • 8.
    Busch, Michael
    et al.
    Institute of Theoretical Chemistry, Ulm University, Oberberghof 7, 89081 Ulm, Germany.
    Sotoudeh, Mohsen
    Institute of Theoretical Chemistry, Ulm University, Oberberghof 7, 89081 Ulm, Germany.
    The role of exact exchange on the structure of water dimer radical cation: Hydrogen bond vs hemibond2023In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 159, no 3, article id 034303Article in journal (Refereed)
  • 9.
    Buser, Michael
    et al.
    Physics Department, University of Texas, Austin, TX 78712, United States.
    Frommhold, Lothar
    Physics Department, University of Texas, Austin, TX 78712, United States.
    Gustafsson, Magnus
    Department of Chemistry, University of Colorado, Boulder, CO 80309-0215, United States.
    Moraldi, Massimo
    Dipartimento di Fisica, Universitá di Firenze, Unitá di Firenze, I-50019 Sesto Fiorentino, via G. Sansone 1, Italy.
    Champagne, Mark H.
    Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States.
    Hunt, Katherine L.C.
    Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States.
    Far-infrared absorption by collisionally interacting nitrogen and methane molecules2004In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 121, no 6, p. 2616-2621Article in journal (Refereed)
  • 10.
    Fakhardji, Wissam
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Szabo, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Physics and Materials Science, University of Luxembourg, Esch-sur-Alzette L-1511, Luxembourg.
    El-Kader, M.S.A.
    Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza 12211, Egypt. Department of Physics, Faculty of Sciences and Humanity Studies, Huraimla, Shaqra University, Shaqra, Saudi Arabia.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Molecular dynamics calculations of collision-induced absorption in a gas mixture of neon and krypton2020In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 152, no 23, article id 234302Article in journal (Refereed)
    Abstract [en]

    We continue the development of the in-house molecular dynamics software package SpaCIAL and test it for the computation of the collision-induced absorption coefficients for a neon (Ne) and krypton (Kr) gas mixture. An apodization procedure for the dipole autocorrelation function is implemented and tested. We also carry out a statistical study of the convergence rate with respect to ensemble size. The resulting absorption coefficients show a good accordance with quantum mechanical results. Comparison with laboratory measurements shows agreement within 10%–20% at T = 295 K. At T = 480 K, a larger difference of 40%–80% is observed, which can presumably be explained by experimental uncertainties. For the study, an empirical (Barker, Fisher, and Watts) interaction-potential [Mol. Phys. 21, 657 (1971)] for Ne–Kr has been developed. Ab initio {coupled cluster with singles and doubles (triples) [CCSD(T)]} potentials for Ne–Ne, Kr–Kr, and Ne–Kr have been computed, as well as the CCSD(T) interaction-induced Ne–Kr dipole moment curve.

  • 11.
    Fakhardji, Wissam
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Szabo, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    El-Kader, M.S.A.
    Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza, Egypt. Department of Physics, Faculty of Sciences and Humanity Studies, Huraimla, Shaqra University, Shaqra, Saudi Arabia.
    Haskopoulos, Anastasios
    Department of Chemistry, University of Patras, Patras, Greece.
    Maroulis, George
    Department of Chemistry, University of Patras, Patras, Greece.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Collision-induced absorption in Ar–Kr gas mixtures: A molecular dynamics study with new potential and dipole data2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 151, no 14, article id 144303Article in journal (Refereed)
    Abstract [en]

    We have implemented a scheme for classical molecular dynamics simulations of collision-induced absorption. The program has been applied to a gas mixture of argon (Ar) and krypton (Kr). The simulations are compared with accurate quantum dynamical calculations. The comparisons of the absorption coefficients show that classical molecular dynamics is correct within 10% for photon wave numbers up to 220 cm−1 at a temperature of 200 K for this system. At higher temperatures, the agreement is even better. Molecular dynamics accounts for many-body interactions, which, for example, give rise to continuous dimer formation and destruction in the gas. In this way, the method has an advantage compared with bimolecular classical (trajectory) treatments. The calculations are carried out with a new empirical Ar–Kr pair potential. This has been obtained through extensive analysis of experimental thermophysical and transport properties. We also present a new high level ab initio Ar–Kr potential curve for comparison, as well as ab initio interaction-induced dipole curves computed with different methods. In addition, the Ar–Kr polarizability and hyperpolarizability are reported. A comparison of the computed absorption spectra with an experiment taken at 300 K shows satisfactory agreement although a difference in absolute magnitude of 10%–15% persists. This discrepancy we attribute mainly to experimental uncertainty.

  • 12.
    Genovese, L.
    et al.
    CEA, INAC, SP2M, L-Sim, 38054 Grenoble Cedex 9, France.
    Neelov, A.
    Institut für Physik, Universität Basel, 4056 Basel, Klingelbergstr. 82, Switzerland.
    Goedecker, S.
    Institut für Physik, Universität Basel, 4056 Basel, Klingelbergstr. 82, Switzerland.
    Deutsch, T.
    CEA, INAC, SP2M, L-Sim, 38054 Grenoble Cedex 9, France.
    Ghasemi, S. A.
    Institut für Physik, Universität Basel, 4056 Basel, Klingelbergstr. 82, Switzerland.
    Willand, A.
    Institut für Physik, Universität Basel, 4056 Basel, Klingelbergstr. 82, Switzerland.
    Caliste, D.
    CEA, INAC, SP2M, L-Sim, 38054 Grenoble Cedex 9, France.
    Zilberberg, O.
    Institut für Physik, Universität Basel, 4056 Basel, Klingelbergstr. 82, Switzerland.
    Rayson, Mark
    Institut für Physik, Universität Basel, 4056 Basel, Klingelbergstr. 82, Switzerland.
    Bergman, A.
    CEA, INAC, SP2M, L-Sim, 38054 Grenoble Cedex 9, France.
    Schneider, R.
    Technische Universität Berlin, Juni 136, D-10623 Berlin, Sekretariat MA 8-1, Str. des 17, Germany.
    Daubechies wavelets as a basis set for density functional pseudopotential calculations2008In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 129, article id 014109Article in journal (Refereed)
  • 13.
    Glaz, Waldemar
    et al.
    Nonlinear Optics Division, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań.
    Bancewicz, Tadeusz
    Nonlinear Optics Division, Faculty of Physics, Adam Mickiewicz University.
    Godet, Jean Luc
    Laboratoire de Photonique D'Angers, Université D'Angers.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Haskopoulos, Anastasios
    Department of Chemistry, University of Patras.
    Maroulis, George
    Department of Chemistry, University of Patras.
    Effects of anisotropic interaction-induced properties of hydrogen-rare gas compounds on rototranslational Raman scattering spectra: Comprehensive theoretical and numerical analysis2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 145, no 3, article id 34303Article in journal (Refereed)
    Abstract [en]

    A comprehensive study is presented of many aspects of the depolarized anisotropic collision induced (CI) component of light scattered by weakly bound compounds composed of a dihydrogen molecule and a rare gas (Rg) atom, H2-Rg. The work continues a series of earlier projects marking the revival of interest in linear light scattering following the development of new highly advanced tools of quantum chemistry and other theoretical, computational, and experimental means of spectral analyses. Sophisticated ab initio computing procedures are applied in order to obtain the anisotropic polarizability component's dependence on the H2-Rg geometry. These data are then used to evaluate the CI spectral lines for all types of Rg atoms ranging from He to Xe (Rn excluded). Evolution of the properties of CI spectra with growing polarizability/masses of the complexes studied is observed. Special attention is given to the heaviest, Kr and Xe based, scatterers. The influence of specific factors shaping the spectral lines (e.g., bound and metastable contribution, potential anisotropy) is discussed. Also the share of pressure broadened allowed rotational transitions in the overall spectral profile is taken into account and the extent to which it is separable from the pure CI contribution is discussed. We finish with a brief comparison between the obtained results and available experimental data

  • 14.
    Gustafsson, Magnus
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Classical calculations of radiative association in absence of electronic transitions2013In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, no 7, article id 74308Article in journal (Refereed)
  • 15.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Formation of NaCl through radiative association: Computations accounting for non-adiabatic dynamics2020In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 153, no 11, article id 114305Article in journal (Refereed)
    Abstract [en]

    The radiative association (RA) rate constant is computed for the formation of the diatomic sodium chloride (NaCl) molecule in the temperature interval 1 K–30 K. At these temperatures, RA of NaCl through non-adiabatic dynamics is important. A scattering program has been implemented to carry out calculations of RA cross sections, accounting for coupled dynamics on the lowest ionic and the lowest neutral diabatic 1Σ+ states. The study shows that the non-adiabatic treatment gives a cross section that exceeds that of conventional adiabatic dynamics by one to four orders of magnitude. The contribution to the RA rate constant from Na and Cl approaching each other in the A1Π state has also been computed using an established quantum mechanical method. Ab initio data from the literature have been used for the potential energy curves, the diabatic coupling, and the electric dipole moments of NaCl.

  • 16.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Antipov, Sergey V.
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Franz, Jan
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden; Mulliken Center for Theoretical Chemistry, University of Bonn, 53115 Bonn, Beringstr. 4-6, Germany.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Refined theoretical study of radiative association: Cross sections and rate constants for the formation of SiN2012In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, no 10, article id 104301Article in journal (Refereed)
  • 17.
    Gustafsson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Forrey, Robert C.
    Pennsylvania State University, Reading, USA.
    Semiclassical methods for calculating radiative association rate constants for different thermodynamic conditions: Application to formation of CO, CN, and SiN2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, ISSN 0021-9606, Vol. 150, no 22, article id 224301Article in journal (Refereed)
    Abstract [en]

    It is well-known that resonances can serve as a catalyst for molecule formation. Rate constants for resonance-induced molecule formation are phenomenological as they depend upon the mechanism used to populate the resonances. Standard treatments assume tunneling from the continuum is the only available population mechanism, which means long-lived quasibound states are essentially unpopulated. However, if a fast resonance population mechanism exists, the long-lived quasibound states may be populated and give rise to a substantial increase in the molecule formation rate constant. In the present work, we show that the semiclassical formula of Kramers and ter Haar [Bull. Astron. Inst. Neth. 10, 137 (1946)] may be used to compute rate constants for radiative association in the limit of local thermodynamic equilibrium. Comparisons are made with quantum mechanical and standard semiclassical treatments, and results are shown for two limits which provide upper and lower bounds for the six most important radiative association reactions leading to the formation of CO, CN, and SiN. These results may have implications for interstellar chemistry in molecular clouds, where the environmental and thermodynamic conditions often are uncertain.

  • 18.
    Gustafsson, Magnus
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    The HD–He complex: Interaction-induced dipole surface and infrared absorption spectra2001In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 115, no 12, p. 5427-5432Article in journal (Refereed)
    Abstract [en]

    The collision-induced dipole surface of an HD molecule interacting with an He atom is derived from the ab initio dipole data of the H2–He complex [Gustafsson et al., J. Chem. Phys. 113, 3641, (2000)]. Collision-induced absorption spectra of gaseous mixtures of deuterium hydride and helium in the rotational and fundamental bands of HD are calculated, for comparison with an existing measurement taken at a temperature of 77 K. To that end, we integrate the close-coupled, radial Schrödinger equations, accounting for the anisotropy of the HD–He interaction potential. The computed absorption spectra generally agree reasonably well with the observed spectral profiles and intensities of the collision-induced spectra. We also consider the interference phenomena of the HD permanent dipole with the interaction-induced, supramolecular dipole by computing the wings of various R(j) lines and of the P1(1) line in single, binary collision limit. For comparison, the line broadening and shift for the P and R line shape parameters are also computed using the impact approximation. The close-coupled treatment of our calculation of the spectral profiles accounts for rotational level mixing in a nonperturbative manner. The treatment is fully quantum-mechanical and takes into account single binary collisions of HD and He.

  • 19.
    Gustafsson, Magnus
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Bailly, Denise
    Labaratoire de Photophysique Moléculaire, CNRS, Campus d’Orsay, France.
    Bouanich, Jean-Pierre
    Labaratoire de Photophysique Moléculaire, CNRS, Campus d’Orsay, France.
    Brodbeck, Claude
    Labaratoire de Photophysique Moléculaire, CNRS, Campus d’Orsay, France.
    Collision-induced absorption in the rototranslational band of dense hydrogen gas2003In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 119, no 23, p. 12264-12270Article in journal (Refereed)
    Abstract [en]

    Measurements of the H2–H2 collision-induced absorption spectra at temperatures of 297.5 and 77.5 K are reported in the frequency range from 1900 to 2260 cm−1 at gas densities ranging from 51 to 610 amagat. Ab initio calculations of the absorption are carried out for comparison with the measurements. In these calculations, for the lower temperature close-coupled equations describe the H2–H2scattering in the presence of a weak electromagnetic radiation field; the anisotropy of the H2–H2interaction is accounted for. For the room temperature calculations, the isotropic potential approximation is employed. Agreement of measured and calculated spectral shapes is observed. However, in the far wing, at large frequencies (≳2000 cm−1), discrepancies of measured and calculated spectral intensities are observed which are somewhat larger than the combined, estimated uncertainties of theory and measurement. These differences remain unexplained at this stage.

  • 20.
    Gustafsson, Magnus
    et al.
    Department of Chemistry, University of Gothenburg, SE 412 96 Gothenburg, Sweden.
    Frommhold, Lothar
    Department of Physics, University of Texas, Austin, TX 78712-1081, United States.
    Li, Xiaoping
    Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States.
    Hunt, Katherine L.C.
    Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States.
    Roto-translational Raman spectra of pairs of hydrogen molecules from first principles2009In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 130, no 16, article id 164314Article in journal (Refereed)
  • 21.
    Gustafsson, Magnus
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Meyer, Wilfried
    Fachbereich Chemie, Universität Kaiserslautern, Germany.
    Infrared absorption spectra by H2–He collisional complexes: The effect of the anisotropy of the interaction potential2000In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 113, no 9, p. 3641-3650Article in journal (Refereed)
    Abstract [en]

    As an extension of previous work which was based on the isotropic interaction approximation, absorption spectra in the rotational and fundamental bands of H2, induced by collisions with He, are calculated by numerical integration of the close-coupled Schrödinger equation to account for the anisotropy of the interaction potential. A refined quantum chemical dipole surface of interactingH2–He pairs is also obtained with an extended grid of molecular geometries. This dipole surface agrees generally well with previous results, but is smaller by about 5% in the isotropic overlap term which is significant only in the fundamental band. The effects of the anisotropy of the interaction are to reduce the peak intensities of the Q and S lines by roughly 10% and to increase absorption in the far wings by a similar amount. The accuracy of the dipole surface as well as that of the ab initiointeraction potential that enters the calculations of the spectra are believed to permit the prediction of absolute spectral intensities with an accuracy of about ±5%. Comparisons with the available measurements show very good agreement of the shapes of the spectral profiles, but the absolute intensities differ by up to 10% in some cases. These remaining differences between theory and measurements appear to be random and are generally smaller than the differences among comparable measurements. Our results should therefore provide a reliable basis for predicting absorption by H2–He pairs for temperatures and frequencies for which no laboratory measurements exist. This fact is of a special interest, for example, for the spectroscopic analyses of the atmospheres of the outer planets.

  • 22.
    Gustafsson, Magnus
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Meyer, Wilfried
    Fachbereich Chemie, Universität Kaiserslautern, Germany.
    The H2–H complex: Interaction-induced dipole surface and infrared absorption spectra2003In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 118, no 4, p. 1667-1472Article in journal (Refereed)
    Abstract [en]

    A quantum chemical dipole surface of interacting H2–H pairs is obtained and collision-induced absorption spectra are computed for temperatures from 200 to 1000 K and frequencies from 0 to 6000 cm−1. The effect of the anisotropy of the potential energy is investigated and turns out to be almost negligible at the temperature for which a close-coupled quantum calculation was done. The smallness of the effect stems from the short range character of the anisotropic potential components for H2–H. Accordingly the isotropic potential approximation could be applied in most of the present calculations. The accuracy of the dipole surface as well as that of the ab initiopotential energy surface that enters the calculations of the spectra are believed to permit prediction of absolute spectral intensities with an accuracy in the 5% range.

  • 23.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Monge-Palacios, Manuel
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden; Departamento de Quimica Fisica, Universidad de Extremadura, 06071 Badajoz, Spain.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    The rate constant for radiative association of HF: Comparing quantum and classical dynamics2014In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 18, article id 184301Article in journal (Refereed)
  • 24.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado, United States.
    Skodje, Rex T.
    Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei, Taiwan.
    The state-to-state-to-state model for direct chemical reactions: Application to D+H2 →hD+H2006In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 124, no 14, article id 144311Article in journal (Refereed)
  • 25.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Skodje, Rex T.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Zhang, Jianyang
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Dai, Dongxu
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Harich, Steven A.
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Wang, Xiuyan
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Yang, Xueming
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Erratum: Observing the stereodynamics of chemical reactions using randomly oriented molecular beams ( Journal of Chemical Physics (2006) 124 (241105))2006In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 125, no 22, article id 229901Article in journal (Other academic)
    Abstract [en]

    A new method is demonstrated to study the stereodynamics of simple chemical reactions that does not require the use of oriented (or aligned) molecular beams or measurements of the orientation state of product molecules. Instead, it is shown that by numerically combining accurate measurements of the state-to-state differential cross section for two or more rotational states of the reagent molecule, the separate contribution from the individual helicity states can be extracted. New molecular beam experiments are conducted for the D+H2→HD+Hreaction that confirm the validity of the method.

  • 26.
    Gustafsson, Magnus
    et al.
    Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, PO Box 23-166, Taiwan; Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, United States.
    Skodje, Rex T.
    Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, PO Box 23-166, Taiwan; Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, United States.
    Zhang, Jianyang
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, 457 Zhongshan Road, China.
    Dai, Dongxu
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, 457 Zhongshan Road, China.
    Harich, Steven A.
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, 457 Zhongshan Road, China.
    Wang, Xiuyan
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, 457 Zhongshan Road, China.
    Yang, Xueming
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, 457 Zhongshan Road, China.
    Observing the stereodynamics of chemical reactions using randomly oriented molecular beams2006In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 124, article id 241105Article in journal (Refereed)
  • 27.
    Głaz, Waldemar
    et al.
    Nonlinear Optics Division, Faculty of Physics, Adam Mickiewicz University, 61-614 Poznán, Umultowska 85, Poland.
    Bancewicz, Tadeusz
    Nonlinear Optics Division, Faculty of Physics, Adam Mickiewicz University, 61-614 Poznán, Umultowska 85, Poland.
    Godet, Jean-Luc
    Laboratoire de Photonique D'Angers, Université D'Angers, 49045 Angers, 2 boulevard Lavoisier, France.
    Gustafsson, Magnus
    Department of Chemistry and Molecular Biology, University of Gothenburg, SE 412 96 Gothenburg, Sweden.
    Maroulis, George
    Department of Chemistry, University of Patras, GR-26500 Patras, Greece.
    Haskopoulos, Anastasios
    Department of Chemistry, University of Patras, GR-26500 Patras, Greece.
    Intermolecular polarizabilities in H2-rare-gas mixtures (H 2-He, Ne, Ar, Kr, Xe): Insight from collisional isotropic spectral properties2014In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 141, no 7, article id 74315Article in journal (Refereed)
  • 28.
    Hochberg, David
    et al.
    Centro de Astrobiología, Consejo Superior de Investigaciones Científicas, Instituto Nacional de T́cnica Aeroespacial (CSIC-INTA).
    Zorzano, María Paz
    Centro de Astrobiología, Consejo Superior de Investigaciones Científicas, Instituto Nacional de T́cnica Aeroespacial (CSIC-INTA).
    Morán, Federico
    Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense de Madrid.
    Spatiotemporal patterns driven by autocatalytic internal reaction noise2005In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 122, no 21, article id 214701Article in journal (Refereed)
    Abstract [en]

    The influence that intrinsic local-density fluctuations can have on solutions of mean-field reaction-diffusion models is investigated numerically by means of the spatial patterns arising from two species that react and diffuse in the presence of strong internal reaction noise. The dynamics of the Gray-Scott (GS) model [P. Gray and S. K. Scott, Chem. Eng. Sci. 38, 29 (1983); P. Gray and S. K. Scott, Chem. Eng. Sci.39, 1087 (1984); P. Gray and S. K. Scott,J. Phys. Chem. 89, 22 (1985)] with a constant external source is first cast in terms of a continuum field theory representing the corresponding master equation. We then derive a Langevin description of the field theory and use these stochastic differential equations in our simulations. The nature of the multiplicative noise is specified exactly without recourse to assumptions and turns out to be of the same order as the reaction itself, and thus cannot be treated as a small perturbation. Many of the complex patterns obtained in the absence of noise for the GS model are completely obliterated by these strong internal fluctuations, but we find novel spatial patterns induced by this reaction noise in the regions of parameter space that otherwise correspond to homogeneous solutions when fluctuations are not included

  • 29. Hoffmann, F.M.
    et al.
    Paul, Jan
    A FT-IRAS study of the vibrational properties of CO adsorbed on Cu/Ru(001): I. The structural and electronic properties of Cu1987In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 86, no 5, p. 2990-2996Article in journal (Refereed)
  • 30. Hoffmann, F.M.
    et al.
    Paul, Jan
    A FT-IRAS study of the vibrational properties of CO adsorbed on Cu/Ru(001): II: The dispersion of copper1987In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 87, no 3, p. 1857-1865Article in journal (Refereed)
    Abstract [en]

    The dispersion of copper adsorbed on a Ru(001) substrate has been investigated by using Fourier transform-infrared reflection absorption spectroscopy (FT-IRAS) and carbon monoxide as a molecular probe. Copper films evaporated at 85 K show a drastically different CO adsorption behavior compared to annealed films and exhibit a variety of adsorption sites. Characteristic C-O stretching frequencies allow us to identify small copper clusters of 1-4 atoms (2138-2123 cm-1), two-dimensional (2120-2110 cm-1) and three-dimensional (2098 cm-1) copper aggregates. After annealing to 250 K copper films at sub- and monolayer coverages form well-ordered small two- and three-dimensional copper aggregates. Formation of the epitaxial monolayer or islands of copper (2082 cm-1) requires a surprizingly mild annealing temperature of 350 K. Further annealing to 540 K results in increasing domain size of the copper islands or annealing of defect sites of the epitaxial monolayer. Multilayer coverages of copper evaporated at 85 K exhibit C-O stretching frequencies found for high-index copper single crystal surfaces, e.g., (211) and (755). This indicates a large number of surface steps and protruding copper atoms associated with rough films. Annealing to 540 K results in a smooth copper layer with preferential (111) orientation (2075 cm-1). The vibrational data presented here for Cu-Ru(001) agree well with previous reports of CO adsorption on copper single crystals, supported or evaporated films, and matrix-isolated clusters. They further allow us to determine the dispersion of supported Cu-Pt and Cu-Ni catalysts from data in the literature.

  • 31. Larsson, Andreas
    et al.
    Greer, James C.
    National Microelectronics Research Centre (NMRC), University College, Lee Maltings, Prospect Row, Cork.
    Harneit, Wolfgang
    Hahn-Meitner Institute, Glienicker Str. 100, D-14109 Berlin.
    Weidinger, Alois
    Hahn-Meitner Institute, Glienicker Str. 100, D-14109 Berlin.
    Phosphorous trapped within buckminsterfullerene2002In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 116, no 18, p. 7849-7854Article in journal (Refereed)
    Abstract [en]

    The chemical, spin, and thermodynamic properties of endohedral phosphorous were studied. A model for the interaction between the trapped group V atom and the fullerene cage was also discussed. It was observed that the repulsion between the group V atom's valence shell and the fullerene cage result in an exothermic binding of the atom within the cage.

  • 32. Larsson, Andreas
    et al.
    Tong, Longyu
    NMRC, University College, Lee Maltings, Cork.
    Cheng, Tongwei
    NMRC, University College, Lee Maltings, Cork.
    Nolan, Michael
    NMRC, University College, Lee Maltings, Cork.
    Greer, James C.
    NMRC, University College, Lee Maltings, Cork.
    Basis set study for the calculation of electronic excitations using Monte Carlo configuration interaction2001In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 114, no 1, p. 15-22Article in journal (Refereed)
    Abstract [en]

    A recipe for the calculation of excited states was presented, which constituted a significant step forward in making accurate excited state calculations. An acceptable energy difference between experimental and calculated energies to be less than 100 meV were also defined. The importance of a balanced description of the excited states and the ground state was emphasized and the resulting electronic transitions were compared with experimental values.

  • 33.
    Li, Yunguo
    et al.
    Applied Material Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH).
    Ahuja, Rajeev B.
    Applied Material Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH).
    Larsson, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Communication: Origin of the difference between carbon nanotube armchair and zigzag ends2014In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 9, article id 91102Article in journal (Refereed)
    Abstract [en]

    In this work, we have found that the difference between armchair and zigzag ends of carbon nanotubes (CNTs) does not pertain at close study for individual bonds and thus alternative strategies need to be developed to reach the ultimate goals in selective growth. Based on first-principles simulations, the difference between binding strengths for CNTs of different chirality was investigated using hydrogen dissociation energies at their passivated ends. When all H atoms are removed collectively we find the well-known difference: that armchair bonds are much weaker than zigzag ones, which is typically seen for both CNT ends and graphene edges. However, when individual H atoms are removed we find almost no difference in hydrogen dissociation energies, small difference in bond lengths, which by association means small difference in C-C and M-C binding energies. We show convincingly that the difference in binding energy between armchair and zigzag ends is due to a fragment stabilization effect that is only manifested when all (or several neighbouring) bonds are broken. This is because at armchair ends/edges neighbouring dangling bonds can pair-up to form C≡C triple bonds that constitute a considerable stabilization effect compared to the isolated dangling bonds at zigzag ends/edges. Consequently, in many processes, e.g., catalytic growth where bonds are normally created/broken sequentially, not collectively, the difference between armchair and zigzag ends/edges cannot be used to discriminate growth of one type over the other to achieve chiral selective growth. Strategies are discussed to realize chirality selective growth in the light of the results presented, including addition of C2-fragments to favor armchair tubes

  • 34.
    Mazza, Francesco
    et al.
    Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Thornquist, Ona
    Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Castellanos, Leonardo
    Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Butterworth, Thomas
    Faculty of Science and Engineering, Maastricht University, Paul Henri Spaaklaan 1, 6229 GS Maastricht, The Netherlands.
    Richard, Cyril
    Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS–Université Bourgogne Franche-Comté, 9 Avenue Alain Savary, BP 47 870, F-21078 Dijon Cedex, France.
    Boudon, Vincent
    Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS–Université Bourgogne Franche-Comté, 9 Avenue Alain Savary, BP 47 870, F-21078 Dijon Cedex, France.
    Bohlin, Alexis
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    The ro-vibrational ν2 mode spectrum of methane investigated by ultrabroadband coherent Raman spectroscopy2023In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 158, no 9, article id 094201Article in journal (Refereed)
    Abstract [en]

    We present the first experimental application of coherent Raman spectroscopy (CRS) on the ro-vibrational ν2 mode spectrum of methane (CH4). Ultrabroadband femtosecond/picosecond (fs/ps) CRS is performed in the molecular fingerprint region from 1100 to 2000 cm−1, employing fs laser-induced filamentation as the supercontinuum generation mechanism to provide the ultrabroadband excitation pulses. We introduce a time-domain model of the CH4 ν2 CRS spectrum, including all five ro-vibrational branches allowed by the selection rules Δv = 1, ΔJ = 0, ±1, ±2; the model includes collisional linewidths, computed according to a modified exponential gap scaling law and validated experimentally. The use of ultrabroadband CRS for in situ monitoring of the CH4 chemistry is demonstrated in a laboratory CH4/air diffusion flame: CRS measurements in the fingerprint region, performed across the laminar flame front, allow the simultaneous detection of molecular oxygen (O2), carbon dioxide (CO2), and molecular hydrogen (H2), along with CH4. Fundamental physicochemical processes, such as H2 production via CH4 pyrolysis, are observed through the Raman spectra of these chemical species. In addition, we demonstrate ro-vibrational CH4 v2 CRS thermometry, and we validate it against CO2 CRS measurements. The present technique offers an interesting diagnostics approach to in situ measurement of CH4-rich environments, e.g., in plasma reactors for CH4 pyrolysis and H2 production.

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  • 35. Paul, Jan
    et al.
    Hoffmann, F.M.
    Alkali promoted CO bond weakening on aluminum: a comparison with transition metal surfaces1987In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 86, no 9, p. 5188-5195Article in journal (Refereed)
    Abstract [en]

    Data on the adsorption and decomposition of carbon monoxide on alkali promoted Al(100) are presented. CO dissociates on the potassium or sodium promoted surface and aluminum oxide and aluminum carbide form after annealing to 700 K. At intermediate temperatures EELS show alkali-CO complexes with vibrational frequencies ranging from 1060 to 2060 cm-1. A band at 1750 cm-1 was assigned to CO molecules coordinated to bulk potassium. CO vibrational spectra as well as work function measurements reveal an altered alkali dispersion as a function of preannealing temperature. Comparisons are made between the surfaces of aluminum and transition metals with respect to (i) alkali adsorption, (ii) hybridization between metal d states and CO π orbitals, (iii) the magnitude of unscreened (long-range) perturbations, and finally (iv) the energetics of carbide and oxide formation. Potassium but not sodium atoms bind strongly to aluminum carbide (Td>700 K). We suggest that potassium is rare among alkali metals not in its ability to promote CO dissociation but in preventing a downshift of the C 2pz orbital and thus carbide to graphite transformation.

  • 36.
    Pilkington, Georgia A.
    et al.
    Surface and Corrosion Science, Department of Chemistry, KTH Royal Institute of Technology.
    Harris, Kathryn
    System and Component Design, Department of Machine Design, KTH Royal Institute of Technology.
    Bergendal, Erik
    Surface and Corrosion Science, Department of Chemistry, KTH Royal Institute of Technology.
    Reddy, Akepati Bhaskar
    System and Component Design, Department of Machine Design, KTH Royal Institute of Technology.
    Pålsson, Gunnar K.
    Department of Physics and Astronomy, Division of Materials Physics, Uppsala University.
    Vorobiev, Alexei
    Department of Physics and Astronomy, Division of Materials Physics, Uppsala University.
    Antzutkin, Oleg N.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Glavatskih, Sergei
    System and Component Design, Department of Machine Design, KTH Royal Institute of Technology.
    Rutland, Mark W.
    Surface and Corrosion Science, Department of Chemistry, KTH Royal Institute of Technology.
    Electro-responsivity of ionic liquid boundary layers in a polar solvent revealed by neutron reflectance2018In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 148, article id 193806Article in journal (Refereed)
    Abstract [en]

    Using neutron reflectivity, the electro-responsive structuring of the non-halogenated ionic liquid (IL) trihexyl(tetradecyl)phosphonium-bis(mandelato)borate, [P6,6,6,14][BMB], has been studied at a gold electrode surface in a polar solvent. For a 20% w/w IL mixture, contrast matched to the gold surface, distinct Kiessig fringes were observed for all potentials studied, indicative of a boundary layer of different composition to that of the bulk IL-solvent mixture. With applied potential, the amplitudes of the fringes from the gold-boundary layer interface varied systematically. These changes are attributable to the differing ratios of cations and anions in the boundary layer, leading to a greater or diminished contrast with the gold electrode, depending on the individual ion scattering length densities. Such electro-responsive changes were also evident in the reflectivities measured for the pure IL and a less concentrated (5% w/w) IL-solvent mixture at the same applied potentials, but gave rise to less pronounced changes. These measurements, therefore, demonstrate the enhanced sensitivity achieved by contrast matching the bulk solution and that the structure of the IL boundary layers formed in mixtures is strongly influenced by the bulk concentration. Together these results represent an important step in characterising IL boundary layers in IL-solvent mixtures and provide clear evidence of electro-responsive structuring of IL ions in their solutions with applied potential.

  • 37.
    Shen, G.
    et al.
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lu, X.
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    A hybrid perturbed-chain SAFT density functional theory for representing fluid behavior in nanopores2013In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, no 22, p. 224706-Article in journal (Refereed)
    Abstract [en]

    A hybrid statistical mechanical model, which is fully consistent with the bulk perturbed-chain statistical associating fluid theory (PC-SAFT) in describing properties of fluids, was developed by coupling density functional theory with PC-SAFT for the description of the inhomogeneous behavior of real chain molecules in nanopores. In the developed model, the modified fundamental measure theory was used for the hard sphere contribution; the dispersion free energy functional was represented with weighted density approximation by averaging the density in the range of interaction, and the chain free energy functional from interfacial statistical associating fluid theory was used to account for the chain connectivity. Molecular simulation results of the density profile were compared with model prediction, and the considerable agreement reveals the reliability of the proposed model in representing the confined behaviors of chain molecules in an attractive slit. The developed model was further used to represent the adsorptions of methane and carbon dioxide on activated carbons, in which methane and carbon dioxide were modeled as chain molecules with the parameters taken from the bulk PC-SAFT, while the parameters of solid surface were obtained from the fitting of gas adsorption isotherms measured experimentally. The results show that the model can reliably reproduce the confined behaviors of physically existing substances in nanopores.

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  • 38.
    Shen, Gulou
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    A hybrid perturbed-chain SAFT density functional theory for representing fluid behavior in nanopores: Mixtures2013In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 139, no 19, article id 194705Article in journal (Refereed)
    Abstract [en]

    The perturbed-chain statistical associating fluid theory (PC-SAFT) density functional theory developed in our previous work was extended to the description of inhomogeneous confined behavior in nanopores for mixtures. In the developed model, the modified fundamental measure theory and the weighted density approximation were used to represent the hard-sphere and dispersion free energy functionals, respectively, and the chain free energy functional from interfacial statistical associating fluid theory was used to account for the chain connectivity. The developed model was verified by comparing the model prediction with molecular simulation results, and the agreement reveals the reliability of the proposed model in representing the confined behaviors of chain mixtures in nanopores. The developed model was further used to predict the adsorption of methane-carbon dioxide mixtures on activated carbons, in which the parameters of methane and carbon dioxide were taken from the bulk PC-SAFT and those for solid surface were determined from the fitting to the pure-gas adsorption isotherms measured experimentally. The comparison of the model prediction with the available experimental data of mixed-gas adsorption isotherms shows that the model can reliably reproduce the confined behaviors of physically existing mixtures in nanopores

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  • 39.
    Shen, Gulou
    et al.
    Huaiyin Institute of Technology, China.
    Zhang, Di
    Huaiyin Institute of Technology, China.
    Hu, Yongke
    Huaiyin Institute of Technology, China.
    Zhang, Xiaojie
    Huaiyin Institute of Technology, China.
    Zhou, Feng
    Huaiyin Institute of Technology, China.
    Qian, Yunhua
    Huaiyin Institute of Technology, China.
    Lu, Xiaohua
    Nanjing Tech University, China.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Effect of surface roughness on partition of ionic liquids in nanopores by a perturbed-chain SAFT density functional theory2022In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 157, no 1, article id 014701Article in journal (Refereed)
    Abstract [en]

    In this work, the distribution and partition behavior of ionic liquids (ILs) in nanopores with rough surfaces are investigated by a two-dimensional (2D) classical density functional theory model. The model is consistent with the equation of state that combines the perturbed-chain statistical associating fluid theory and the mean spherical approximation theory for bulk fluids. Its performance is verified by comparing the theoretical predictions with the results from molecular simulations. The fast Fourier transform and a hybrid iteration method of Picard iteration and Anderson mixing are used to efficiently obtain the solution of density profile for the sizable 2D system. The molecular parameters for IL-ions are obtained by fitting model predictions to experimental densities of bulk ILs. The model is applied to study the structure and partition of the ILs in nanopores. The results show that the peak of the density profile of counterions near a rough surface is much higher than that near a smooth surface. The adsorption of counterions and removal of co-ions are enhanced by surface roughness. Thus, the nanopore with a rough surface can store more charge. At low absolute surface potential, the partition coefficient for ions on rough surfaces is lower than that on smooth surfaces. At high absolute surface potential, increasing surface roughness leads to an increase in the partition coefficient for counterions and a decrease in the partition coefficient for co-ions.

  • 40.
    Szabo, Peter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    A surface-hopping method for semiclassical calculations of cross sectionsfor radiative association with electronic transitions2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, article id 094308Article in journal (Refereed)
    Abstract [en]

    A semiclassical method based on surface-hopping techniques is developed to model the dynamics of radiative association with electronic transitions. It can be proven that this method is an extension of the established semiclassical formula used in the characterization of diatomic molecule-formation. Our method is tested for diatomic molecules. It gives the same cross sections as the former semiclassical formula but, contrary to the former method, it allows us to follow the fate of the trajectories after the emission of a photon. This means that we can characterize the rovibrational states of the stabilized molecules. Using semiclassical quantization, we can obtain quantum state-resolved cross sections or emission spectra for the radiative association process. The calculated semiclassical state-resolved spectra show general agreement with the result of quantum mechanical perturbation theory. Furthermore, our surface-hopping model is not only applicable for the description of radiative association but it can be used for semiclassical characterization of any molecular process where spontaneous emission occurs

  • 41.
    Szabo, Peter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium; Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Avenue Circulaire 3, 1180 Brussels, Belgium.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Polyatomic radiative association by quasiclassical trajectory calculations: Formation of HCN and HNC molecules in H + CN collisions2023In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 159, no 14, article id 144112Article in journal (Refereed)
    Abstract [en]

    We have developed the polyatomic extension of the established [M. Gustafsson, J. Chem. Phys. 138, 074308 (2013)] classical theory of radiative association in the absence of electronic transitions. The cross section and the emission spectrum of the process is calculated by a quasiclassical trajectory method combined with the classical Larmor formula which can provide the radiated power in collisions. We have also proposed a Monte Carlo scheme for efficient computation of ro-vibrationally quantum state resolved cross sections for radiative association. Besides the method development, the global potential energy and dipole surfaces for H + CN collisions have been calculated and fitted to test our polyatomic semiclassical method.

  • 42.
    Verkhoturov, Stanislav V.
    et al.
    Department of Chemistry, Texas A&M University.
    Czerwinski, Bartlomiej
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Verkhoturov, Dmitriy S.
    Department of Chemistry, Texas A&M University, College Station, Texas 77843-3144, USA.
    Geng, Sheng
    Department of Chemistry, Texas A&M University, College Station, Texas 77843-3144, USA.
    Delcorte, Arnaud
    nstitute of Condensed Matter and Nanosciences - Bio and Soft Matter (IMCN/BSMA), Universit ́ e Catholique de Louvain, 1 Croix du Sud, B-1348 Louvain-la-Neuve, Belgium.
    Schweikert, Emile A.
    Department of Chemistry, Texas A&M University, College Station, Texas 77843-3144, USA.
    Ejection-ionization of molecules from free standing graphene2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 8, article id 084308Article in journal (Refereed)
    Abstract [en]

    We present the first data on emission of C60stimulated by single impacts of 50 keV C602+on the self-assembled molecular layer of C60deposited on free standing 2 layer graphene. The yield,Y, of C60emitted in the transmission direction is 1.7%. To characterize the ejection and ionization of molecules,we have measured the emission of C60from the surface of bulk C60(Y= 3.7%) and from a singlelayer of C60deposited on bulk pyrolytic graphite (Y= 3.3%). To gain insight into the mechanism(s) ofejection, molecular dynamic simulations were performed. The scenario of the energy deposition andejection of molecules is different for the case of graphene due to the confined volume of projectile-analyte interaction. In the case of 50 keV C602+impacts on graphene plus C60, the C atoms of theprojectile collide with those of the target. The knocked-on atoms take on a part of the kinetic energyof the projectile atoms. Another part of the kinetic energy is deposited into the rim around the impactsite. The ejection of molecules from the rim is a result of collective movement of the molecules andgraphene membrane, where the membrane movement provides the impulse for ejection. The efficientemission of the intact molecular ions implies an effective ionization probability of intact C60. Theproposed mechanism of ionization involves the tunneling of electrons from the vibrationally exitedarea around the hole to the ejecta

  • 43.
    Verkhoturov, Stanislav V.
    et al.
    Department of Chemistry, Texas AandM University, College Station.
    Geng, Sheng
    Department of Chemistry, Texas AandM University, College Station.
    Czerwinski, Bartlomiej
    Universite Catholique de Louvain, Institute of Condensed Matter and Nanosciences - Bio and Soft Matter, Louvain-la-Neuve.
    Young, Amanda E.
    Materials Characterization Facility, Texas AandM University.
    Delcorte, Arnaud
    Universite Catholique de Louvain, Institute of Condensed Matter and Nanosciences - Bio and Soft Matter, Louvain-la-Neuve.
    Schweikert, Emile A.
    Department of Chemistry, Texas AandM University, College Station.
    Single impacts of keV fullerene ions on free standing graphene: Emission of ions and electrons from confined volume2015In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 143, no 16, article id 164302Article in journal (Refereed)
    Abstract [en]

    We present the first data from individual C60 impacting one to four layer graphene at 25 and 50 keV. Negative secondary ions and electrons emitted in transmission were recorded separately from each impact. The yields for Cn - clusters are above 10% for n ≤ 4, they oscillate with electron affinities and decrease exponentially with n. The result can be explained with the aid of MD simulation as a post-collision process where sufficient vibrational energy is accumulated around the rim of the impact hole for sputtering of carbon clusters. The ionization probability can be estimated by comparing experimental yields of Cn - with those of Cn 0 from MD simulation, where it increases exponentially with n. The ionization probability can be approximated with ejecta from a thermally excited (3700 K) rim damped by cluster fragmentation and electron detachment. The experimental electron probability distributions are Poisson-like. On average, three electrons of thermal energies are emitted per impact. The thermal excitation model invoked for Cn - emission can also explain the emission of electrons. The interaction of C60 with graphene is fundamentally different from impacts on 3D targets. A key characteristic is the high degree of ionization of the ejecta

  • 44.
    Verkhoturov, Stanislav V.
    et al.
    Department of Chemistry, Texas A&M University, College Station, Texas, USA.
    Gołuński, Mikołaj
    Department of Physics, Jagiellonian University, Kraków, Poland.
    Verkhoturov, Dmitriy S.
    Department of Chemistry, Texas A&M University, College Station, Texas, USA.
    Czerwinski, Bartlomiej
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Eller, Michael J.
    Department of Chemistry, Texas A&M University, College Station, Texas, USA.
    Geng, Sheng
    Department of Chemistry, Texas A&M University, College Station, Texas, USA.
    Postawa, Zbigniew
    Department of Physics, Jagiellonian University, Kraków, Poland.
    Schweikert, Emile A.
    Department of Chemistry, Texas A&M University, College Station, Texas, USA.
    Hypervelocity cluster ion impacts on free standing graphene: Experiment, theory, and applications2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 150, no 16, article id 160901Article in journal (Refereed)
    Abstract [en]

    We present results from experiments and molecular dynamics (MD) simulations obtained with C60 and Au400 impacting on free-standing graphene, graphene oxide (GO), and graphene-supported molecular layers. The experiments were run on custom-built ToF reflectron mass spectrometers with C60 and Au-LMIS sources with acceleration potentials generating 50 keV C2+ 60 and 440–540 keV Au4+ 400. Bombardmentdetection was in the same mode as MD simulation, i.e., a sequence of individual projectile impacts with separate collection/identification of the ejecta from each impact in either the forward (transmission) or backward (reflection) direction. For C60 impacts on single layer graphene, the secondary ion (SI) yields for C2 and C4 emitted in transmission are ∼0.1 (10%). Similar yields were observed for analyte-specific ions from submonolayer deposits of phenylalanine. MD simulations show that graphene acts as a trampoline, i.e., they can be ejected without destruction. Another topic investigated dealt with the chemical composition of free-standing GO. The elemental composition was found to be approximately COH2. We have also studied the impact of Au400 clusters on graphene. Again SI yields were high (e.g., 1.25 C /impact). 90–100 Au atoms evaporate off the exiting projectile which experiences an energy loss of ∼72 keV. The latter is a summation of energy spent on rupturing the graphene, ejecting carbon atoms and clusters and a dipole projectile/hole interaction. The charge distribution of the exiting projectiles is ∼50% neutrals and ∼25% either negatively or positively charged. We infer that free-standing graphene enables detection of attomole to zeptomole deposits of analyte via cluster-SI mass spectrometry

  • 45.
    Wang, Y.L.
    et al.
    Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology.
    Sarman, Sten
    Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology.
    Kloo, Lars
    Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Glavatskih, Sergei
    System and Component Design, Department of Machine Design, KTH Royal Institute of Technology.
    Laaksonen, Aatto
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Solvation structures of water in trihexyltetradecylphosphonium-orthoborate ionic liquids2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 145, no 6, article id 064507Article in journal (Refereed)
    Abstract [en]

    Atomistic molecular dynamics simulations have been performed to investigate effective interactions of isolated water molecules dispersed in trihexyltetradecylphosphonium-orthoborate ionic liquids (ILs). The intrinsic free energy changes in solvating one water molecule from gas phase into bulk IL matrices were estimated as a function of temperature, and thereafter, the calculations of potential of mean force between two dispersed water molecules within different IL matrices were performed using umbrella sampling simulations. The systematic analyses of local ionic microstructures, orientational preferences, probability and spatial distributions of dispersed water molecules around neighboring ionic species indicate their preferential coordinations to central polar segments in orthoborate anions. The effective interactions between two dispersed water molecules are partially or totally screened as their separation distance increases due to interference of ionic species in between. These computational results connect microscopic anionic structures with macroscopically and experimentally observed difficulty in completely removing water from synthesized IL samples and suggest that the introduction of hydrophobic groups to central polar segments and the formation of conjugated ionic structures in orthoborate anions can effectively reduce residual water content in the corresponding IL samples

  • 46.
    Öström, Jonatan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Bezrukov, Dmitry S.
    Department of Chemistry, M. V. Lomonosov Moscow State University.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Erratum: “Reaction rate constant for radiative association of CF+” [J. Chem. Phys. 144, 044302 (2016)]2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 150, no 24, article id 249901Article in journal (Other academic)
  • 47.
    Öström, Jonatan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Bezrukov, Dmitry S.
    Department of Chemistry, M. V. Lomonosov Moscow State University.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Reaction rate constant for radiative association of CF+2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 144, no 4, article id 44302Article in journal (Refereed)
    Abstract [en]

    Reaction rate constants and cross sections are computed for the radiative association of carbon cations (C+) and fluorine atoms (F) in their ground states. We consider reactions through the electronic transition 11Π → X1Σ+ and rovibrational transitions on the X1Σ+ and a3Π potentials. Semiclassical and classical methods are used for the direct contribution and Breit–Wigner theory for the resonance contribution. Quantum mechanical perturbation theory is used for comparison. A modified formulation of the classical method applicable to permanent dipoles of unequally charged reactants is implemented. The total rate constant is fitted to the Arrhenius–Kooij formula in five temperature intervals with a relative difference of <3%. The fit parameters will be added to the online database KIDA. For a temperature of 10–250 K, the rate constant is about 10−21 cm3 s−1, rising toward 10−16 cm3 s−1 for a temperature of 30 000 K.

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