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• 201.
Laboratoire de Physique Corpusculaire, Université Blaise Pascal Clermont-Ferrand.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Preon trinity: a schematic model of leptons, quarks and heavy vector bosons2002Inngår i: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 60, nr 2, s. 188-194Artikkel i tidsskrift (Fagfellevurdert)

Quarks, leptons and heavy vector bosons are suggested to be composed of stable spin- (1/2) preons, existing in three flavours, combined according to simple rules. Straightforward consequences of an SU(3) preon-flavour symmetry are the conservation of three lepton numbers, oscillations and decays between some neutrinos, and the mixing of the d and s quarks, as well as of the vector fields W0 and B0. We find a relation between the Cabibbo and Weinberg mixing angles, and predict new (heavy) leptons, quarks and vector bosons, some of which might be observable at the Fermilab Tevatron and the future CERN LHC. A heavy neutrino might even be visible in existing data from the CERN LEP facility.

• 202. Dugne, Jean-Jacques
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Higgs pain? Take a preon!1997Inngår i: Proceedings of the Meeting on 'The Fundamental Structure of Matter' and 'Tests of the Electroweak Symmetry Breaking', Ouranoupolis, Greece, May 1997, 1997Konferansepaper (Fagfellevurdert)

The Higgs mechanism is the favourite cure for the main problem with electroweak unification, namely how to reconcile a gauge theory with the need for massive gauge bosons. This problem does not exist in preon models for quark and lepton substructure with composite $Z^0$ and $W$s, which, consequently, also avoid all other theoretical complications and paradoxes with the Higgs mechanism. We present a new, minimal preon model, which explains the family structure, and predicts several new, heavy quarks, leptons and vector bosons. Our preons obey a phenomenological supersymmetry, but without so-called squarks and sleptons, since this SUSY is effective only on the composite scale.

• 203. Dugne, Jean-Jacques
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Preon Trinity: a new model of leptons and quarks1999Inngår i: Beyond the desert 1999: accelerator, non-accelerator, and space approaches into the next millennium ; proceedings of the Second International Conference on Particle Physics Beyond the Standard Model, Castle Ringberg, Germany, 6 - 12 June 1999 / [ed] Hans Volker Klapdor-Kleingrothaus, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 1999Konferansepaper (Fagfellevurdert)

A new model for the substructure of quarks, leptons and weak gauge bosons, is discussed. It is based on three fundamental and absolutely stable spin-1/2 preons. Its preon flavour SU(3) symmetry leads to a prediction of nine quarks, nine leptons and nine heavy vector bosons. One of the quarks has charge $-4e/3$, and is speculated to be the top quark (whose charge has not been measured). The flavour symmetry leads to three conserved lepton numbers in all known weak processes, except for some neutrinos, which might either oscillate or decay. There is also a (Cabibbo) mixing of the $d$ and $s$ quarks due to an internal preon-antipreon annihilation channel. An identical channel exists inside the composite $Z^0$, leading to a relation between the Cabibbo and Weinberg mixing angles.

• 204. Dugne, Jena-Jacques
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Preon trinity1998Rapport (Annet vitenskapelig)

We present a new minimal model for the substructure of all known quarks, leptons and weak gauge bosons, based on only three fundamental and stable spin-1/2 preons. As a consequence, we predict three new quarks, three new leptons, and six new vector bosons. One of the new quarks has charge $-4e/3$. The model explains the apparent conservation of three lepton numbers, as well as the so-called Cabibbo-mixing of the $d$ and $s$ quarks, and predicts electromagnetic decays or oscillations between the neutrinos $\bar{\nu}_{\mu}$ ($\nu_{\mu}$) and $\nu_e$ ($\bar{\nu}_e$). Other neutrino oscillations, as well as rarer quark mixings and CP violation can come about due to a small quantum-mechanical mixing of two of the preons in the quark and lepton wave functions.

• 205.
Luleå tekniska universitet.
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
Full potential calculations on the electron band structures of Sphalerite, Pyrite and Chalcopyrite2003Inngår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 206, nr 1-4, s. 300-313Artikkel i tidsskrift (Fagfellevurdert)

The metal contents of ore can be as low as 0.4%m This means sophisticated methods of enrichment have to be applied. Better understanding of the processes of flotation and leaching may lead to higher yields and less damage to the environment. The bulk electronic structures of Sphalerite, Pyrite and Chalcopyrite have been calculated within an ab initio, full potential, density functional approach. The exchange term was approximated with the Dirac exchange functional, the Vosko-Wilk-Nusair parameterization of the Cepler-Alder free electron gas was used for correlation and linear combinations of Gaussian type orbitals were used as basis functions. The Sphalerite (zinc blend) band gap was calculated to be direct with a width of 2.23 eV. The Sphalerite valence band was 5.2 eV wide and composed of a mixture of sulfur and zinc orbitals. The band below the valence band located around -6.2 eV was mainly composed of Zn 3d orbitals. The S 3s orbitals gave rise to a band located around -12.3 eV. Pyrite was calculated to be a semiconductor with an indirect band gap of 0.51 eV, and a direct gap of 0.55 eV. The valence band was 1.25 eV wide and mainly composed of non-bonding Fe 3d orbitals. The band below the valence band was 4.9 eV wide and composed of a mixture of sulfur and iron orbitals. Due to the short inter-atomic distance between the sulfur dumbbells, the S 3s orbitals in Pyrite were split into a bonding and an anti-bonding range. Chalcopyrite was predicted to be a conductor, with no band-crossings at the Fermi level. The bands at -13.2 eV originate from the sulfur 3s orbitals and were quite similar to the sulfur 3s bands in Sphalerite, though somewhat shifted to lower energy. The top of the valence band consisted of a mixture of orbitals from all the atoms. The lower part of the same band showed metal character. Computational modeling as a tool for illuminating the flotation and leaching processes of Pyrite and Chalcopyrite, in connection with surface science experiments, is discussed.

• 206.
Kungliga tekniska högskolan, KTH.
Rice University, Houston. University of Hongkong. Umeå universitet. Chuparosa Research, Mesa, Arizona. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
The effect of water on the Fe3+/Fe2+ reduction potential of heme2000Inngår i: Biochemical and Biophysical Research Communications - BBRC, ISSN 0006-291X, E-ISSN 1090-2104, Vol. 268, nr 3, s. 683-687Artikkel i tidsskrift (Fagfellevurdert)

Hemeproteins can act as catalysts, oxygen carriers or electron conductors. The ferric/ferrous reduction potential Em7 of iron in the center of the prosthetic group ranges from negative values for peroxidases to an extreme positive value for cytochrome a3 with Hb and Mb in the middle [1]. Proteins exercise their influence on Em7 in several ways: via substituents at the periphery of the chelate structure, via the proximal ligand, and via interaction with the surrounding medium, amino acid side chains, or polar solvents. Work on recombined proteins and 2,4-substituted free hemes documented that the first two effects are additive [2]. For the third effect, models of the dielectric media on a molecular level have been successfully applied [3-5]. Em7 has also been empirically correlated to the degree of heme exposure to water [6-8]. The apoprotein/porphyrin and water/porphyrin interfaces are complementary since water molecules fill any empty space in the crevice and surround any pertinent part of heme outside the protein boundary. The present work links to this idea by a combination of statistical mechanics simulations and quantum mechanical calculations comparing heme in water with heme in an apolar environment. Our results show that polarization of the porphyrin π-electron cloud by the field from water dipoles influences Em7. The dominant effect of this and other determinates of iron electron availability is perturbations of delocalized electron density in the porphyrin chelate, reproduced by a model where the prosthetic group is treated as a disc of uniform electron density. The present work is also of interest since the interfacial energy constitutes the main barrier for heme-protein separation [9-11].

• 207. Edholm, O.
The barrier for heme-protein separation estimated by non-equilibrium molecular dynamics simulations1998Inngår i: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 291, nr 5-6, s. 501-508Artikkel i tidsskrift (Fagfellevurdert)

In heme-containing proteins the heme group is usually non-covalently bound in a pocket. Molecular dynamics (MD) simulations have been performed to estimate the barrier height for heme-protein separation. In simulations of myoglobin dissolved in water, a force has been applied to pull the heme out of the binding pocket. With forces above 0.5 nN, the heme group is easily pulled out of the pocket in times of the order of tens of picoseconds. With weaker forces, heme release becomes too slow to be monitored in an MD simulation covering a couple of hundred picoseconds. These results are consistent with a free energy barrier to heme release of about 100 kJ/mol. The results show that the main energetic change that occurs during the release is a conversion of heme/protein Lennard-Jones energy into heme/water Lennard-Jones energy. The release is essentially barrierless in energy indicating that the main part of the barrier is entropic.

• 208.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
NASA Ames Research Center.
Correlation of subsurface ice content and gully locations on Mars; testing the shallow aquifer theory of gully formation2006Inngår i: Lunar and planetary science, XXXVII: papers presented to the Thirty-seventh lunar and planetary science conference / [ed] Stephen J. Mackwell, Houston, Tex: Lunar and planetary institute , 2006Konferansepaper (Annet vitenskapelig)
• 209. Eilam, G.
Small angle production from nuclear and nucleon targets1980Inngår i: Lettere al Nuovo Cimento della Società Italiana di Fisica, ISSN 0375-930X, Vol. 27, s. 299-Artikkel i tidsskrift (Fagfellevurdert)
• 210. Ekelin, Svante
Hadron pT correlations in quark jets1986Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 56, nr 22, s. 2428-2428Artikkel i tidsskrift (Fagfellevurdert)
• 211. Ekelin, Svante
Large-pT protons from constituent diquark scattering1984Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 149, nr 6, s. 509-513Artikkel i tidsskrift (Fagfellevurdert)

Recent data from the CERN ISR on the fractional proton yield in pp collisions are explained within the Stockholm diquark model. Describing the proton as a u(ud)0 system, the observed high magnitude and fall-off pT, θ and √s of the proton yield are natural consequences of constituent diquark elastic scattering. The pT and θ dependence favour a value of around 10 GeV2/c2 for the size parameter in the diquark form factor, corresponding to a diquark rms radius of around 0.2 fm. This is consistent with earlier results of the model applied to deep inelastic lepton-nucleon scattering and e+e- annihilation

• 212. Ekelin, Svante
Baryons from diquarks in e+e- annihilation1983Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 28, nr 1, s. 257-259Artikkel i tidsskrift (Annet vitenskapelig)

We find experimental support for the view that diquarks appear only as spin-0 objects. When their production rate in the color field of a quark from e+e- annihilation is described by the appropriate Schwinger formula for scalars, it turns out that they must be substantially lighter than earlier believed in order to explain the baryon yield.

• 213. Ekelin, Svante
Indications of hard diquarks in e+e- annihilation1984Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 30, nr 11, s. 2310-2315Artikkel i tidsskrift (Fagfellevurdert)

It is suggested that very small spin-0 diquarks are directly produced in e+e- annihilation and then fragment into leading baryons and other hadrons. The most influential diquark is the charmed diquark (uc), due to its high charge. It gives a sizable contribution to the hadronic R factor and to the two-jet angular distribution in the energy region W=4-8 GeV. At these energies, a careful study of Λ production would provide the best additional test of the model.

• 214.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
Cosmic dust and heavy neutrinos2007Doktoravhandling, med artikler (Annet vitenskapelig)

This Doctoral thesis treats two subjects. The first subject is the impact of early dust on the cosmic microwave background (CMB). The dust that is studied comes from the first generation of stars, which were hot and short-lived, ending their lives as giant supernovae. In the supernova explosions, heavy elements, produced through the fusion in the stars, were ejected into the interstellar medium. These heavy elements condensed to form dust, which can absorb and thus perturb the CMB radiation. The dust contribution to this radiation is calculated and found negligible. However, since the dust is produced within structures (like galaxy clusters), it will have a spatial correlation that could be used to detect it. This correlation is calculated with relevant assumptions. The planned Planck satellite could eventually detect and thus confirm this correlation. The second subject is heavy neutrinos and their impact on the diffuse gamma ray background. Neutrinos heavier than M_Z /2 ~ 45 GeV are not excluded by particle physics data. Stable neutrinos heavier than this might contribute to the cosmic gamma ray background through annihilation in distant galaxies as well as to the dark matter content of the universe. The evolution of the heavy neutrino density in the universe is calculated as a function of its mass, M_N, and then the subsequent gamma ray spectrum from annihilation of distant N-Nbar (from 0 < z < 5). The evolution of the heavy neutrino density in the universe is calculated numerically. In order to obtain the enhancement due to structure formation in the universe, the distribution of N is approximated to be proportional to that of dark matter in the GalICS model. The calculated gamma ray spectrum is compared to the measured EGRET data. A conservative exclusion region for the heavy neutrino mass is 100 to 200 GeV, both from EGRET data and our re-evalutation of the Kamiokande data. The heavy neutrino contribution to dark matter is found to be at most 15%. Finally, heavy neutrinos are considered within the context of a preon model for composite leptons and quarks, where such particles are natural. The consequences of these are discussed, with emphasis on existing data from the particle accelerator LEP at CERN. A numerical method for optimizing variable cuts in particle physics is also included in the thesis.

• 215.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
Dust in the early universe2005Licentiatavhandling, med artikler (Annet vitenskapelig)

This Licentiate thesis treats the impact of early dust on the Cosmic Microwave Background (CMB). The dust that is studied comes from the first generation of stars, which were hot and short-lived, ending their lives as giant supernovæ. In the supernova explosions, heavy elements, produced through the fusion in the stars, were ejected into the interstellar medium. These heavy elements condensed to form dust, which can absorb and thus perturb the Cosmic Microwave Background radiation. The dust contribution to this radiation is calculated and found negligible. However, as the dust will be produced within structures (like galaxy clusters), it will have a spatial correlation that could be used to detect it. This correlation is calculated using relevant assumptions. The planned Planck satellite is likely to be able to measure and thus confirm this correlation.

• 216.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
Laboratoire d’Astrophysique, Observatoire de Grenoble.
Dust from reionization2004Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 425, s. 9-14Artikkel i tidsskrift (Fagfellevurdert)

The possibility that population III stars have reionized the Universe at redshifts greater than 6 has recently gained momentum with WMAP polarization results. Here we analyse the role of early dust produced by these stars and ejected into the intergalactic medium. We show that this dust, heated by the radiation from the same population III stars, produces a submillimetre excess. The electromagnetic spectrum of this excess could account for a significant fraction of the FIRAS (Far Infrared Absolute Spectrophotometer) cosmic far infrared background above 700 micron. This spectrum, a primary anisotropy (Delta T) spectrum times the nu2 dust emissivity law, peaking in the submillimetre domain around 750 micron, is generic and does not depend on other detailed dust properties. Arcminute-scale anisotropies, coming from inhomogeneities in this early dust, could be detected by future submillimetre experiments such as Planck HFI.

• 217.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
Laboratoire d’Astrophysique, Observatoire de Grenoble. Université Lyon 1, Centre de Recherche Astrophysique de Lyon, Observatoire de Lyon.
Dust distribution during reionization2007Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 476, s. 1145-1150Artikkel i tidsskrift (Fagfellevurdert)

Context. The dust produced by the first generation of stars will be a foreground to cosmic microwave background.Aims. In order to evaluate the effect of this early dust, we calculate the power spectrum of the dust emission anisotropies and compare it with the sensitivity limit of the Planck satellite.Methods. The spatial distribution of the dust is estimated through the distribution of dark matter.Results. At small angular scales l ≥ 1000 the dust signal is found to be noticeable with the Planck detector for certain values of dust lifetime and production rates. The dust signal is also compared to sensitivities of other instruments. The early dust emission anisotropies are finally compared to those of local dustand they are found to be similar in magnitude at mm wavelengths.

• 218.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Mass limits for heavy neutrinos2008Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 479, nr 2, s. 347-353Artikkel i tidsskrift (Fagfellevurdert)

Context. Neutrinos heavier than MZ/2 ∼ 45 GeV are not excluded by particle physics data. Stable neutrinos heavier than this might contribute to the cosmic gamma ray background through annihilation in distant galaxies, as well as to the dark matter content of the universe.Aims. We calculate the evolution of the heavy neutrino density in the universe as a function of its mass, MN, and then the subsequent gamma ray spectrum from annihilation of distant N ¯N (from 0 < z < 5).Methods. The evolution of the heavy neutrino density in the universe is calculated numerically. To obtain the enhancement due to structure formation in the universe, we approximate the distribution of N to be proportional to that of dark matter in the GalICS model. The calculated gamma ray spectrum is compared to the measured EGRET data.Results. A conservative exclusion region for the heavy neutrino mass is 100 to 200 GeV, both fromEGRET data and our re-evalutation of the Kamiokande data. The heavy neutrino contribution to dark matter is found to be at most 15%.

• 219.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Swerea MEFOS AB. SSAB.
Possibility to combine exergy with other process integration methods for a steelmaking case2010Inngår i: PRES 2010, 13th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction / [ed] Jirí J. Klemeš; Hon Loong Lam; Petar S. Varbanov, AIDIC Servizi S.r.l. , 2010, s. 1375-1380Konferansepaper (Fagfellevurdert)

The energy system of Luleå consists of the steel plant, a local CHP using process gases from the plant and the district heating system. Process integration work to improve the efficiency of the system is presently carried out by mathematical programming using a MILP tool (reMIND). Further improvements would need an improved possibility of the tool to consider the thermodynamic quality of the energy flows. This project aims to include exergy parameters in the node equations and object functions. This has been carried out for a test case, including a part of the system. Programming principles and some results are described.

• 220.
Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University.
Laboratoire de photonique d'Angers, Université d'Angers. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Chemistry, University of Patras.
Multi-property isotropic intermolecular potentials and predicted spectral lineshapes of collision-induced absorption (CIA), collision-induced light scattering (CILS) and collision-induced hyper-Rayleigh scattering (CIHR) for H2Ne, −Kr and −Xe2018Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 209, s. 232-242Artikkel i tidsskrift (Fagfellevurdert)

Quantum mechanical lineshapes of collision-induced absorption (CIA), collision-induced light scattering (CILS) and collision-induced hyper-Rayleigh scattering (CIHR) at room temperature (295 K) are computed for gaseous mixtures of molecular hydrogen with neon, krypton and xenon. The induced spectra are detected using theoretical values for induced dipole moment, pair-polarizability trace and anisotropy, hyper-polarizability and updated intermolecular potentials. Good agreement is observed for all spectra when the literature and the present potentials which are constructed from the transport and thermo-physical properties are used.

• 221.
Astronomy Unit, Queen Mary and Westfield College, University of London.
Luleå tekniska universitet.
General relativistic 1 + 3 orthonormal frame approach1997Inngår i: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 14, nr 9, s. 2673-2695Artikkel i tidsskrift (Fagfellevurdert)

The dynamical equations of an extended 1 + 3 orthonormal frame approach to the relativistic description of spacetime geometries are explicitly presented and discussed in detail. In particular, the Bianchi identities for the Weyl curvature tensor occur in a fully expanded form, as they are given a central role in the extended formalism. It is shown how one can naturally introduce local coordinates, both in the 1 + 3 threading and the ADM 3 + 1 slicing context. By specializing the general 1 + 3 dynamical equations it is demonstrated how a number of problems of interest can be obtained. In particular, the simplest choices of spatial frames for spatially homogeneous cosmological models, locally rotationally symmetric spacetime geometries, cosmological models with an Abelian isometry group G2 and 'silent' dust cosmological models are discussed.

• 222.
Astronomy Unit, Queen Mary and Westfield College, University of London.
Luleå tekniska universitet. Department of Applied Mathematics, University of Fort Hare. Department of Applied Mathematics, University of Cape Town. School of Mathematical Studies, Portsmouth University.
Integrability of irrotational silent cosmological models1997Inngår i: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 14, nr 5, s. 1151-1162Artikkel i tidsskrift (Fagfellevurdert)

We revisit the issue of integrability conditions for the irrolational silent cosmological models. We formulate the problem both in 1 + 3 covariant and 1 + 3 orthonormal frame notation and show that there exists a series of constraint equations that need to be satisfied. These conditions hold identically for FLRW-linearized silent models, but not in the general exact nonlinear case. Thus there is a linearization instability and it is highly unlikely that there is a large class of silent models We conjecture that there are no spatially inhomogeneous solutions with Weyl curvature of Petrov type I and indicate further issues that await clarification.

• 223.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
CNR-IFN, Istituto di Fotonica e Nanotecnologie, CSMFO Lab. & FBK-CMM. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia. Meridionale Impianti SpA. Laboratoire des Technologies Innovantes, LTI, Département de Génie industriel ENSA – Tanger. Laboratoire des Technologies Innovantes, LTI, Département de Génie industriel ENSA – Tanger. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia. M. Ferrari . Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Piazza del Viminale . Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia. Institute of Low Temperature and Structure Research, PAS.
Silver doping of silica-hafnia waveguides containing Tb3+/Yb3+ rare earths for downconversion in PV solar cells2016Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 60, s. 264-269Artikkel i tidsskrift (Fagfellevurdert)

The aim of this paper is to study the possibility to obtain an efficient downconverting waveguide which combines the quantum cutting properties of Tb3+/Yb3+ codoped materials with the optical sensitizing effects provided by silver doping. The preparation of 70SiO(2)-30HfO(2) glass and glass-ceramic waveguides by sol-gel route, followed by Ag doping by immersion in molten salt bath is reported. The films were subsequently annealed in air to induce the migration and/or aggregation of the metal ions. Results of compositional and optical characterization are given, providing evidence for the successful introduction of Ag in the films, while the photoluminescence emission is strongly dependent on the annealing conditions. These films could find potential applications as downshifting layers to increase the efficiency of PV solar cells

• 224.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
CSMFO Lab., Istituto di Fotonica e Nanotecnologie CNR. Laboratoire des Technologies Innovantes, LTI, Université Abdelmalek Essâadi, Tanger. Laboratoire des Technologies Innovantes, LTI, Université Abdelmalek Essâadi, Tanger. CSMFO Lab., Istituto di Fotonica e Nanotecnologie CNR. Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Piazza del Viminale . Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi. Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi.
Visible to NIR downconversion process in Tb3+-Yb3+ codoped silica-hafnia glass and glass-ceramic sol-gel waveguides for solar cells2018Inngår i: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 193, s. 44-50Artikkel i tidsskrift (Fagfellevurdert)

The efficiency of photovoltaic solar cells is strongly related to the spectral absorption and photo-conversion properties of the cell's active material, which does not exploit the whole broadband solar spectrum. This mismatch between the spectrum of the solar light and the wavelength dependent cell's response can be partially overcome by using luminescent conversion layers in front or in the back of the solar cell. In this paper, the investigation of Tb3+-Yb3+ co-doped SiO2-HfO2 glass and glass-ceramic waveguides is presented. Due to a down-conversion process based on cooperative energy transfer between one Tb3+ ion and two Yb3+ ions, a blue photon at 488 nm can be divided in two NIR photons at 980 nm. Films with different molar concentrations of rare earths, up to a total amount of [Tb+Yb] = 15%, were prepared by a sol-gel route, using dip-coating deposition on SiO2 substrates. For all the films, the molar ratio [Yb]/[Tb] was taken equal to 4. The comparison of the energy-transfer efficiency between Tb3+ and Yb3+ ions in the glass and in the glass-ceramic materials demonstrated the higher performance of the glass-ceramic, with a maximum quantum transfer efficiency of 179% for the highest rare earth doping concentration. Moreover, experimental results and comparison with proper rate equations modelling showed a linear dependence of the photoluminescence emission intensity for the Yb3+ ions 2F5/22F7/2 transition at 980 nm on the excitation power, indicating a direct transfer process from Tb3+ to Yb3+ ions. The reported waveguides could find applications not only as downconverting filters in transmission but also as efficient solar concentrators in the near-IR spectral region

• 225.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Roma.
Laboratoire des Technologies Innovantes, LTI, Université Abdelmalek Essâadi, Tanger. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Mestre, Venezia. Laboratoire des Technologies Innovantes, LTI, Université Abdelmalek Essâadi, Tanger. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia. Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Roma. Dipartimento di Ingegneria Industriale (DII), Università degli Studi di Padova. Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Roma. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Roma. Department of Chemistry and Chemical Engineering, Chalmers University of Technology. Dipartimento di Ingegneria Industriale (DII), Università degli Studi di Padova. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Mestre, Venezia. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Mestre, Venezia. Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Roma. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Mestre, Venezia. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Roma.
Ag nanoaggregates as efficient broadband sensitizers for Tb3+ ions in silica-zirconia ion-exchanged sol-gel glasses and glass-ceramics2018Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 84, s. 668-674Artikkel i tidsskrift (Fagfellevurdert)

In this paper we report the study of down-shifting silica-zirconia glass and glass-ceramic films doped by Tb3+ ions and Ag nanoaggregates, which combine the typical spectral properties of the rare-earth-ions with the broadband sensitizing effect of the metal nanostructures. Na-Tb co-doped silica-zirconia samples were obtained by a modified sol-gel route. Dip-coating deposition followed by annealing for solvent evaporation and matrix densification were repeated several times, obtaining a homogeneous crack-free film. A final treatment at 700 °C or 1000 °C was performed to control the nanoscale structural properties of the samples, resulting respectively in a glass (G) or a glass-ceramic (GC), where tetragonal zirconia nanocrystals are surrounded by an amorphous silica matrix. Ag introduction was then achieved by ion-exchange in a molten salt bath, followed by annealing in air to control the migration and aggregation of the metal ions. The comparison of the structural, compositional and optical properties are presented for G and GC samples, providing evidence of highly efficient photoluminescence enhancement in both systems, slightly better in G than in GC samples, with a remarkable increase of the green Tb3+ PL emission at 330 nm excitation: 12 times for G and 8 times for GC samples. Furthermore, after Ag-exchange, the shape of Tb3+ excitation resembles the one of Ag ions/nanoaggregates, with a broad significant absorption in the whole UV-blue spectral region. This broadband enhanced downshifting could find potential applications in lighting devices and in PV solar cells.

• 226.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Roma, Italy. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Venezia, Italy.
Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Venezia, Italy. Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Roma, Italy. Istituto di Fotonica e Nanotecnologie del Consiglio Nazionale delle Ricerche (IFN-CNR), Laboratorio CSMFO and Fondazione Bruno Kessler (FBK) Photonics Unit, Trento, Italy. Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Roma, Italy. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Venezia, Italy. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Venezia, Italy. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Venezia, Italy. Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Roma, Italy. Istituto di Fisica Applicata Nello Carrara del Consiglio Nazionale delle Ricerche (IFAC-CNR), Firenze, Italy. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Venezia, Italy. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Roma, Italy. Istituto di Fotonica e Nanotecnologie del Consiglio Nazionale delle Ricerche (IFN-CNR), Laboratorio CSMFO and Fondazione Bruno Kessler (FBK) Photonics Unit, Trento, Italy.
Ag-Sensitized Yb3+ Emission in Glass-Ceramics2018Inngår i: Micromachines, ISSN 2072-666X, E-ISSN 2072-666X, Vol. 9, nr 8, artikkel-id 380Artikkel i tidsskrift (Fagfellevurdert)

Rare earth doped materials play a very important role in the development of many photonic devices, such as optical amplifiers and lasers, frequency converters, solar concentrators, up to quantum information storage devices. Among the rare earth ions, ytterbium is certainly one of the most frequently investigated and employed. The absorption and emission properties of Yb3+ ions are related to transitions between the two energy levels 2F7/2 (ground state) and 2F5/2 (excited state), involving photon energies around 1.26 eV (980 nm). Therefore, Yb3+ cannot directly absorb UV or visible light, and it is often used in combination with other rare earth ions like Pr3+, Tm3+, and Tb3+, which act as energy transfer centres. Nevertheless, even in those co-doped materials, the absorption bandwidth can be limited, and the cross section is small. In this paper, we report a broadband and efficient energy transfer process between Ag dimers/multimers and Yb3+ ions, which results in a strong PL emission around 980 nm under UV light excitation. Silica-zirconia (70% SiO2-30% ZrO2) glass-ceramic films doped by 4 mol.% Yb3+ ions and an additional 5 mol.% of Na2O were prepared by sol-gel synthesis followed by a thermal annealing at 1000 °C. Ag introduction was then obtained by ion-exchange in a molten salt bath and the samples were subsequently annealed in air at 430 °C to induce the migration and aggregation of the metal. The structural, compositional, and optical properties were investigated, providing evidence for efficient broadband sensitization of the rare earth ions by energy transfer from Ag dimers/multimers, which could have important applications in different fields, such as PV solar cells and light-emitting near-infrared (NIR) devices.

• 227.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
School of Physics and Materials for Energy Research Group, University of the Witwatersrand, Johannesburg. Historical Museum of Physics and Study & Research Centre “Enrico Fermi”.
Plasmonic enhanced solar cells: Summary of possible strategies and recent results2018Inngår i: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 82, nr 3, s. 2433-2439Artikkel i tidsskrift (Fagfellevurdert)

Plasmonic structures for light manipulation at sub-wavelength scale have received great interest in the field of photovoltaic (PV) solar cells for their potential to significantly enhance the cell's efficiency.

The performance of any solar cell is determined by the capability to absorb incoming light and produce electric charges, which, in turn, has a number of limiting factors. One is related to the ever-reducing size and acceptance angle of the active region. Another is the limited spectral sensitivity of the active material, which cannot make use of significant parts of the solar spectrum.

Correspondingly, the energy harvesting may be improved in two ways, namely by adopting light trapping schemes and by exploiting spectral modification processes to shift frequencies of the solar spectrum, which are initially not absorbed, into the region of maximum absorption of the cell.

Plasmonic nanoparticles (NPs) can give a significant boost to both these aspects, by scattering and concentrating the electromagnetic field into the active region of the device, and by doing that within specific spectral regions, which can be properly tuned by optimizing the size, shape, distribution of the plasmonic NPs, and by choosing the right surrounding medium.

During the last ten years, many papers have been published on very specific issues, but also on general properties of plasmonics applied to solar cells, with a strong increase between 2006 and 2012, followed by a period of significant, but stable, literature productivity. Given these premises, an organized and schematic summary of the main strategies and of the recent results on the field is given in this review, where different plasmonic approaches are compared and discussed, also by recalling specific examples from the literature and providing a few key conclusions to understand the main aspects and the future perspectives of the field.

• 228.
Luleå tekniska universitet.
Aspects of quarks in exotic matter1999Licentiatavhandling, med artikler (Annet vitenskapelig)

In this licentiate thesis, two different aspects of particle physics have been studied. The results are presented in four papers. In papers I and II, a model for a joint origin of gamma-ray bursts and dark matter is presented. The common denominator is the deconfined state of quarks, the Quark-Gluon Plasma (QGP). We propose that such quark objects surviving the quark-hadron transition in the early universe, constitute the dark matter and that mergers of these objects are the inner engine of gamma-ray bursts. We have computed stability criteria for macroscopic quark objects, as well as the merger frequency assuming a lognormal distribution in size. In paper III, the helicity amplitudes for rare-meson production invirtual gamma-gamma collisions are computed. We show that it is possible to apply a generalised version of the Brodsky-Lepage scheme for exclusive processes in QCD, when computing these amplitudes. In paper IV, we analyse consequences of the new supernova data, suggesting a non-zero vacuum energy density in the universe. We calculate the intrinsic luminosity correction for high-redshift objects such as gamma-ray bursts and quasars. Two different extensions of the Friedmann-Robertson-Walker universe are used; a non-zero cosmological constant and a time-dependent spatially inhomogeneous energy density component (so-called quintessence). The results show a correction of up to 30% for the conventionally computed luminosities.

• 229. Enström, Daniel
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Luminosities of high-redshift objects in an accelerating universe1999Rapport (Annet vitenskapelig)

The results from the Supernova Cosmology Project indicate a relation between cosmic distance and redshift that corresponds to an accelerating Universe, and, as a consequence, the presence of an energy component with negative pressure. This necessitates a re-evaluation of such astrophysical luminosities that have been derived through conventional redshift analyses of, e.g., gamma-ray bursts and quasars. We have calculated corrected luminosity distances within two scenarios; the standard one with a non-zero cosmological constant, and the more recently proposed quintessence'', with a slowly evolving energy-density component. We find luminosity corrections from +30 to -40 per cent for redshifts with $z=0 - 10$. This finding implicates that the SCP data do not, by themselves, require a revision of the current, rather qualitative modeling of gamma-ray bursts and quasar properties.

• 230. Enström, Daniel
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Kungliga tekniska högskolan, KTH.
A Quark matter dominated universe1998Rapport (Annet vitenskapelig)

We present a new scenario for the development of the Universe after the Big Bang, built on the conjecture that a vast majority of the primordial quark matter did not undergo a phase transition to normal nuclear matter, but rather split up into massive quark objects that remained stable. Hence, such primordial quark matter would make up the so-called dark matter. We discuss, mostly in qualitative terms, the consequences for galaxy formation, the origin of normal matter, the occurrence of massive black-holes in galactic centres and the cosmic gamma-ray bursts.

• 231. Enström, Daniel
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Kungliga tekniska högskolan, KTH.
Gamma-Ray Bursts and Dark Matter: a joint origin?1998Konferansepaper (Fagfellevurdert)
• 232.
Istituto per la Microelettronica e i Microsistemi, IMM-CNR.
Istituto per lo Studio dei Materiali Nanostrutturati, ISMN-CNR. Istituto per lo Studio dei Materiali Nanostrutturati, ISMN-CNR. Istituto di Cristallografia, IC-CNR. Istituto di Cristallografia, IC-CNR. Electrochemical Processes Unit, IMDEA Energy Institute, Avda. NMR Unit, Centro de Apoyo Tecnológico, Universidad Rey Juan Carlos. Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Bellaterra. Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Bellaterra. Istituto per la Microelettronica e i Microsistemi, IMM-CNR. Department of Information Engineering, Brescia University. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Inorganic Photocatalytic Enhancement: Activated RhB Photodegradation by Surface Modification of SnO2 Nanocrystals with V2O5-like species2017Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikkel-id 44763Artikkel i tidsskrift (Fagfellevurdert)

SnO2 nanocrystals were prepared by precipitation in dodecylamine at 100 °C, then they were reacted with vanadium chloromethoxide in oleic acid at 250 °C. The resulting materials were heat-treated at various temperatures up to 650 °C for thermal stabilization, chemical purification and for studying the overall structural transformations. From the crossed use of various characterization techniques, it emerged that the as-prepared materials were constituted by cassiterite SnO2 nanocrystals with a surface modified by isolated V(IV) oxide species. After heat-treatment at 400 °C, the SnO2 nanocrystals were wrapped by layers composed of vanadium oxide (IV-V mixed oxidation state) and carbon residuals. After heating at 500 °C, only SnO2 cassiterite nanocrystals were obtained, with a mean size of 2.8 nm and wrapped by only V2O5-like species. The samples heat-treated at 500 °C were tested as RhB photodegradation catalysts. At 10-7 M concentration, all RhB was degraded within 1 h of reaction, at a much faster rate than all pure SnO2 materials reported until now.

• 233.
Istituto per la Microelettronica e i Microsistemi, IMM-CNR, Lecce, Italy.
Istituto per lo Studio dei Materiali Nanostrutturati, ISMN-CNR, Roma, Italy. Istituto per lo Studio dei Materiali Nanostrutturati, ISMN-CNR, Roma, Italy. Istituto di Cristallografia, IC-CNR, Bari, Italy. Istituto di Cristallografia, IC-CNR, Bari, Italy. Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology (BIST), Barcelona, Catalonia, Spain; Catalonia Institute for Energy Research (IREC), Barcelona, Catalonia, Spain. Catalonia Institute for Energy Research (IREC), Barcelona, Catalonia, Spain. Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology (BIST), Barcelona, Catalonia, Spain; ICREA, Barcelona, Catalonia, Spain. Istituto per la Microelettronica e i Microsistemi, IMM-CNR, Lecce, Italy. Department of Information Engineering, Brescia University, Brescia, Italy; SENSOR, Brescia University & CNR INO, Brescia, Italy. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Solvothermal Synthesis, Gas-Sensing Properties, and Solar Cell-Aided Investigation of TiO2-MoOx Nanocrystals2017Inngår i: ChemNanoMat, ISSN 2199-692X, Vol. 3, nr 11, s. 798-807Artikkel i tidsskrift (Fagfellevurdert)

Titania anatase nanocrystals were prepared by sol-gel/solvothermal synthesis in oleic acid at 250 °C, and modified by co-reaction with Mo chloroalkoxide, aimed at investigating the effects on gas-sensing properties induced by tailored nanocrystals surface modification with ultra-thin layers of MoOx species. For the lowest Mo concentration, only anatase nanocrystals were obtained, surface modified by a disordered ultra-thin layer of mainly octahedral MoVI oxide species. For larger Mo concentrations, early MoO2 phase segregation occurred. Upon heat treatment up to 500 °C, the sample with the lowest Mo concentration did not feature any Mo oxide phase segregation, and the surface Mo layer was converted to dense octahedral MoVI oxide. At larger Mo concentrations all segregated MoO2 was converted to MoO3. The two different materials typologies, depending on the Mo concentration, were used for processing gas-sensing devices and tested toward acetone and carbon monoxide, which gave a greatly enhanced response, for all Mo concentrations, to acetone (two orders of magnitude) and carbon monoxide with respect to pure TiO2. For the lowest Mo concentration, dye-sensitized solar cells were also prepared to investigate the influence of anatase surface modification on the electrical transport properties, which showed that the charge transport mainly occurred in the ultra-thin MoOx surface layer.

• 234. Esser, H.G.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Comparison of different methods to characterize thin a-Si:H films1998Inngår i: Modern Developments and Applications in Microbeam Analysis, Wien: Encyclopedia of Global Archaeology/Springer Verlag, 1998, s. 163-170Kapittel i bok, del av antologi (Annet vitenskapelig)
• 235.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Activity: Magnetisation dynamics in ferromagnetic nanostructures2015Konferansepaper (Annet (populærvitenskap, debatt, mm))
• 236.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Activity: Simulating magnetic excitations: from bulk to nanostructures2015Konferansepaper (Annet (populærvitenskap, debatt, mm))
• 237.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Uppsala universitet.
KTH, Royal Institute of Technology, Department of Materials and Nano Physics. Department of Physics and Astronomy, Uppsala University. Department of Physics and Astronomy, Uppsala University. Department of Physics and Astronomy, Uppsala University.
Atomistic spin dynamics and surface magnons2015Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 27, nr 24, artikkel-id 243202Artikkel i tidsskrift (Fagfellevurdert)

Atomistic spin dynamics simulations have evolved to become a powerful and versatile tool for simulating dynamic properties of magnetic materials. It has a wide range of applications, for instance switching of magnetic states in bulk and nano-magnets, dynamics of topological magnets, such as skyrmions and vortices and domain wall motion. In this review, after a brief summary of the existing investigation tools for the study of magnons, we focus on calculations of spin-wave excitations in low-dimensional magnets and the effect of relativistic and temperature effects in such structures. In general, we find a good agreement between our results and the experimental values. For material specific studies, the atomistic spin dynamics is combined with electronic structure calculations within the density functional theory from which the required parameters are calculated, such as magnetic exchange interactions, magnetocrystalline anisotropy, and Dzyaloshinskii-Moriya vectors

• 238.
Department of Physics and Astronomy, Uppsala University.
Uppsala universitet, Department of Physics and Astronomy, Uppsala University. Uppsala universitet, Department of Physics and Astronomy, Uppsala University. Uppsala universitet, Department of Physics and Astronomy, Uppsala University.
Accelerating the switching of magnetic nanoclusters by anisotropy-driven magnetization dynamics2012Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 86, nr 22, artikkel-id 224401Artikkel i tidsskrift (Fagfellevurdert)

In this work, the magnetization dynamics of clusters supported on nonmagnetic substrates is shown to exhibit a complex response when subjected to external magnetic fields. The field-driven magnetization reversal of small Co clusters deposited on a Cu(111) surface has been studied by means of first-principles calculations and atomistic spin dynamics simulations. For applied fields ranging from 1 to 10 Tesla, we observe a coherent magnetization reversal with switching times in the range of several tenths of picoseconds to several nanoseconds, depending on the field strength. We find a nonmonotonous dependence of the switching times with respect to the strength of the applied field, which we prove has its origin in the complex magnetic anisotropy landscape of these low-dimensional systems. This effect is shown to be stable for temperatures around 10 K, and is possible to realize over a range of exchange interactions and anisotropy landscapes. Possible experimental routes to achieve this unique switching behavior are discussed

• 239.
Center for Computational Materials Science, Technical University Vienna.
Hungarian Academy of Sciences, Wigner Research Centre for Physics, Institute for Solid State Physics and Optics. Center for Computational Materials Science, Technical University Vienna. Center for Computational Materials Science, Technical University Vienna. Hungarian Academy of Sciences, Wigner Research Centre for Physics, Institute for Solid State Physics and Optics. Department of Theoretical Physics, Budapest University of Technology and Economics. Materials Science and Technology Division, Oak Ridge National Laboratory. Vienna University of Technology, Center for Computational Materials Science, Technical University Vienna.
Magnetic properties of FeCo nanoclusters on Cu(100: Ab initio calculations2007Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, nr 24, artikkel-id 245432Artikkel i tidsskrift (Fagfellevurdert)

We present ab initio calculations of the magnetic moments and magnetic anisotropy energies of small FeCo clusters of varying composition on top of a Cu(100) substrate. Three different cluster layouts have been considered, namely, 2×2, 3×3, and crosslike pentamer clusters. The ratio of Co atoms with respect to the total number in a chosen cluster ("concentration") was varied and all possible arrangements of the atomic species were taken into account. Calculations have been performed fully relativistic using the embedded-cluster technique in conjunction with the screened Korringa-Kohn- Rostoker method and the magnetocrystalline anisotropy energy (MAE) has been evaluated by means of the magnetic force theorem. A central result of the investigations is that the size of the magnetic moments of the individual Fe and Co atoms and their contributions to the anisotropy energy depend on the position they occupy in a particular cluster and on the type and the number of nearest neighbors. The MAE for the 2×2 and 3×3 clusters varies with respect to the concentration of Co atoms in the same manner as the corresponding monolayer case, whereas the pentamer clusters show a slightly different behavior. Furthermore, for the clusters with an easy axis along a direction in the surface plane, the MAE shows a significant angular dependence.

• 240.
Department of Physics and Astronomy, Uppsala University.
Institut für Physik, Martin-Luther-Universität Halle-Wittenberg. Max-Planck-Institut für Mikrostrukturphysik. Institut für Physik, Martin-Luther-Universität Halle-Wittenberg. Max-Planck-Institut für Festkörperforschung. Institut für Physik, Martin-Luther-Universität Halle-Wittenberg. Naval Research Laboratory, Washington, DC. Institut für Physik, Martin-Luther-Universität Halle-Wittenberg. Max-Planck-Institut für Mikrostrukturphysik.
Indications of weak electronic correlations in SrRuO3 from first-principles calculations2012Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 86, nr 6, artikkel-id 64441Artikkel i tidsskrift (Fagfellevurdert)

We provide, by a detailed first-principles investigation, evidence for weak electronic correlations in SrRuO 3. The magnetism in SrRuO 3, in terms of the equilibrium magnetization and critical temperature, is well described by the generalized gradient approximation. Including Hubbard-type correlations results in worse agreement with experiment

• 241.
Institut de Physique et de Chimie des Matériaux de Strasbourg.
Institut de Physique et de Chimie des Matériaux de Strasbourg.
First principle study of the magnetism of Sr 2CoMoO 6-δ (δ = 0, 1/2) double perovskites2006Inngår i: European Physical Journal B: Condensed Matter Physics, ISSN 1434-6028, E-ISSN 1434-6036, Vol. 54, nr 4, s. 429-434Artikkel i tidsskrift (Fagfellevurdert)

We investigate the electronic structure of bulk Sr 2CoMoO 6-δ double perovskites using the ab initio Full Potential Linearized Augmented Plane Wave method in order to study their magnetic properties within the GGA and GGA+U methods. We discuss the relative stability of ferromagnetic (FM) and antiferromagnetic (AFM) orders (i) without and with taking into account the observed tilting of the oxygen octahedra and (ii) by introducing oxygen vacancies. We show that a very good agreement with experimental results - AFM order for δ= 0 and FM order for δ= 1/2 - is obtained only when the tilting of the oxygen tetrahedra is taking into account and when the GGA+U method is used

• 242.
Vienna University of Technology.
Vienna University of Technology. Budapest University of Technology and Economics. Vienna University of Technology.
Ab initio magneto-optical properties of bcc Ni/Ni(100)2008Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 77, nr 6, artikkel-id 64420Artikkel i tidsskrift (Fagfellevurdert)

The inter- and intralayer contributions to the layer-resolved complex optical conductivity tensor for semi-infinite layered systems are calculated in terms of the Luttinger formula within the spin-polarized relativistic screened Korringa-Kohn-Rostoker method. Ab initio Kerr angles are then obtained for arbitrary geometry and incidence via a 2x2 matrix technique including all multiple reflections and all optical interferences. Applied to in-plane single-domain magnetized bcc Ni/Ni(100), it is proven that the assumed appropriate formula of Kerr angles widely used to explain magneto-optical Kerr effect with rotating magnetic field measurements fully agrees with our ab initio Kerr data. From the experimental Kerr data of Tian [Phys. Rev. Lett. 94, 137210 (2005)], however, it cannot be concluded that the deduced magnetic properties apply for bulk Ni, since about 75% of the contributions to the Kerr rotation angle arise from the surface.

• 243.
Max-Planck-Institut für Mikrostrukturphysik.
Vienna University of Technology, AC²T research GmbH - Austrian Center of Competence for Tribology, Viktor-Kaplan-Straße 2 D, 2700 Wiener Neustadt. Vienna University of Technology, Max-Planck-Institut für Mikrostrukturphysik.
Magneto-optical properties of Co/Ir superstructures on Ir(111)2011Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, nr 1, artikkel-id 14419Artikkel i tidsskrift (Fagfellevurdert)

The fully relativistic spin-polarized screened Korringa-Kohn-Rostoker method is used to evaluate the electronic and magnetic structure as well as the optical conductivity of (ComIrm)n superstructures on Ir(111). By mapping the microscopic optical conductivity tensor onto the macroscopic permittivity tensor and by using the so-called 2×2 matrix technique the surface reflectivity matrices for these systems are then calculated, from which in turn the Kerr rotation and ellipticity angles can be determined. It is found (i) that when varying at a given value of m the number of repetitions n, these angles are linearly proportional to the total magnetic moment, and (ii) that at a frequency of about 3.8 eV the Kerr rotation angles have the largest value, the corresponding maximum being mainly caused by the Ir spacer layers. The optical properties of the free surface of Ir(111), which is considered to check the applied theoretical schemes, turn out to be in good agreement with existing experimental data.

• 244.
Center for Computational Materials Science, Vienna University of Technology.
Vienna University of Technology, Center for Computational Materials Science, Vienna University of Technology. Vienna University of Technology, Center for Computational Materials Science, Vienna University of Technology.
ROTMOKE: An assessment of macroscopic models for bcc Ni/Ni(100)2008Inngår i: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 88, nr 18-20, s. 2765-2775Artikkel i tidsskrift (Fagfellevurdert)

Ab-initio Kerr angles for a multilayer system were calculated by means of Luttinger's formalism within the spin-polarized relativistic screened Korringa-Kohn-Rostoker method by including all multiple reflections and optical interferences via the 2 2 matrix technique. Two further macroscopic models are suggested for a multilayer system; i.e., the two-media approach and the three-media approach. The Kerr angles obtained using the two-media approach show that 75 % of the Kerr rotation angles arise from surface contributions when compared to the 2 2 matrix approach. Furthermore, by comparing the three-media approach to the 2 2 matrix technique it is found that almost 25 % of the Kerr rotation angles are due to interfaces between the atomic layers

• 245.
Center for Computational Materials Science, Vienna University of Technology.
Center for Computational Materials Science, Technical University Vienna. Vienna University of Technology. Institute for Applied Physics, University of Hamburg.
Magnetic properties of single atoms of Fe and Co on Ir(111) and Pt(111)2008Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, nr 18, artikkel-id 184425Artikkel i tidsskrift (Fagfellevurdert)

In using the fully relativistic versions of the embedded cluster and screened Korringa-Kohn-Rostoker methods for semi-infinite systems the magnetic properties of single adatoms of Fe and Co on Ir(111) and Pt(111) are studied. It is found that for Pt(111) Fe and Co adatoms are strongly perpendicularly oriented, while on Ir(111) the orientation of the magnetization is only out of plane for a Co adatom; for an Fe adatom it is in plane. For comparison, the so-called band energy parts of the anisotropy energy of a single layer of Fe and Co on these two substrates are also shown. The obtained results are compared to recent experimental studies using, e.g., the spin-polarized STM technique

• 246.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Molecular dynamics simulations of collision-induced absorption: Implementation in LAMMPS2017Inngår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 810, nr 1, artikkel-id 012031Artikkel i tidsskrift (Fagfellevurdert)

We pursue simulations of collision-induced absorption in a mixture of argon and xenon gas at room temperature by means of classical molecular dynamics. The established theoretical approach (Hartmann et al. 2011 J. Chem. Phys. 134 094316) is implemented with the molecular dynamics package LAMMPS. The bound state features in the absorption spectrum are well reproduced with the molecular dynamics simulation in comparison with a laboratory measurement. The magnitude of the computed absorption, however, is underestimated in a large part of the spectrum. We suggest some aspects of the simulation that could be improved

• 247.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. 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. Department of Chemistry, University of Patras, Patras, Greece. Department of Chemistry, University of Patras, Patras, Greece. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
Collision-induced absorption in Ar–Kr gas mixtures: A molecular dynamics study with new potential and dipole data2019Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 151, nr 14, artikkel-id 144303Artikkel i tidsskrift (Fagfellevurdert)

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.

• 248.
Dipartimento di Fisica Sperimentale, Università di Torino.
Dipartimento di Fisica Sperimentale, Università di Torino. Dipartimento di Fisica Sperimentale, Università di Torino. Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones. Laboratori Nazionali di Legnaro. Laboratori Nazionali di Legnaro.
Growth and characterisation of polymeric amorphous carbon and carbon nitride films from propane2005Inngår i: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 14, nr 3-7, s. 928-933Artikkel i tidsskrift (Fagfellevurdert)

In this work, we report about the deposition of a-C(N):H films by electron-cyclotron-resonance using propane as a carbon precursor. The films generally present high H contents (up to 61 at.%) and large optical gaps. The maximum N content we obtained is 13 at.%. In nitrogenated films, we observed a strong decrease of the stretching intensity of the infrared spectra of the hydrocarbon (CHn) vibrations, even at very low nitrogen content, the H content being still comparable to that of pure a-C:H. The various phenomena that can lead to such an effect are discussed: (i) different type of hydrogen bonding (CHn and NHn) in presence and in absence of nitrogenation; (ii) weakening of the cross-section of the CHn groups in presence of nitrogen; (iii) large presence of non-bonded hydrogen meaning, with this, either the presence of molecular H2 or unbounded hydrogen. In addition, the residual amount of IR absorption due to C-H vibrations shows that, in a-CN:H, C-H bonded and non-bonded hydrogen does coexist. © 2005 Elsevier B.V. All rights reserved.

• 249.
A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of Russian Academy of Sciences.
Kazan (Volga Region) Federal University. A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of Russian Academy of Sciences. A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of Russian Academy of Sciences. A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of Russian Academy of Sciences. A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of Russian Academy of Sciences. A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of Russian Academy of Sciences. A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of Russian Academy of Sciences. CNR-IMM, Bologna Section. CNR-IMM, Bologna Section. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of Russian Academy of Sciences. A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of Russian Academy of Sciences.
Silica Nanospheres Coated by Ultrasmall Ag0 Nanoparticles for Oxidative Catalytic Application2017Inngår i: Colloid and Interface Science Communications, ISSN 2215-0382, Vol. 21, s. 1-5Artikkel i tidsskrift (Fagfellevurdert)

The present work introduces optimal modifiсation of core-shell composite nanomaterial, where small (2–8 nm) Ag0 nanoparticles are deposited onto large (about 140 nm) silica spheres for application in oxidative catalysis. The size of Ag0 and density of its deposition onto silica spheres was modified by the post treatment of initially deposited Ag0 (about 30 nm) by hydrogen peroxide in specific conditions. The comparison of catalytic effect of the post-treated and initial SN-Ag0 in electrochemical phosphonation of benzo(thia)oxazoles by diethyl phosphite in oxidative conditions revealed the difference between the composite nanoparticles. In particular, the post-treated SNs-Ag0 nanoparticles exhibit efficient catalytic effect in oxidative conditions resulting in facile and green method for synthesis of phosphonated benzooxa(thia)zoles, while no catalytic effect is observed under the use of larger Ag0 nanoparticles deposited onto silica spheres. The use of Ag0-based nanomaterial in oxidative catalysis had been never demonstrated before

• 250.
Department of Organic Chemistry University of Pannonia, Institute of Chemistry Egyetem, Veszprém, Hungary.
Department of Organic Chemistry University of Pannonia, Institute of Chemistry Egyetem, Veszprém, Hungary. Department of Analytical Chemistry University of Pannonia, Institute of Chemistry Egyetem, Veszprém, Hungary. University of Pannonia, Institute of Environmental Engineering Egyetem, Veszprém Hungary. Department of Surface Chemistry and Catalysis Hungarian Academy of Sciences, Centre for Energy Research, Budapest, Hungary. Research Centre for Natural Sciences Hungarian Academy of Sciences, Budapest, Hungary. Department of Inorganic Chemistry and MTA-PTE Research Group for Selective Chemical Syntheses University of Pécs, Pécs, Hungary. Department of Organic Chemistry University of Pannonia, Institute of Chemistry Egyetem, Veszprém, Hungary.
Heterogeneous azide–alkyne cycloaddition in the presence of a copper catalyst supported on an ionic liquid polymer/silica hybrid material2018Inngår i: Applied organometallic chemistry, ISSN 0268-2605, E-ISSN 1099-0739, Vol. 32, nr 6, artikkel-id e4343Artikkel i tidsskrift (Fagfellevurdert)

Heterogeneous copper catalysts were prepared by the deposition of CuI on a hybrid material consisting of silica and a polymer with imidazolium moieties. The solid materials were characterised using solid‐phase NMR, Fourier transform infrared, Raman and X‐ray photoelectron spectroscopies and Brunauer–Emmett–Teller measurements. The formation of copper–carbene complexes was proved from Raman spectra and the results were supported by density functional theory calculations. The catalyst could be recycled efficiently with low loss of copper. Metal leaching was proved to be facilitated by the use of conditions typical for a homogeneous system (the presence of a polar solvent or the addition of a tertiary amine). Besides simple model reactions, the best catalyst was found to be suitable for the synthesis of triazoles of more elaborate structure, such as ferrocene or steroid derivatives.

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