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Talwelkar Shimpi, M., Sajjad, M., Öberg, S. & Larsson, J. A. (2023). Physical binding energies using the electron localization function in 4-hydroxyphenylboronic acid co-crystals with aza donors. Journal of Physics: Condensed Matter, 35(50), Article ID 505901.
Open this publication in new window or tab >>Physical binding energies using the electron localization function in 4-hydroxyphenylboronic acid co-crystals with aza donors
2023 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 35, no 50, article id 505901Article in journal (Refereed) Published
Abstract [en]

Binding energies are traditionally simulated using cluster models by computation of each synthon for each individual co-crystal former. However, our investigation of the binding strengths using the electron localization function (ELF) reveals that these can be determined directly from the crystal supercell computations. We propose a new modeling protocol for the computation of physical binding energies directly from bulk simulations using ELF analysis. In this work, we establish a correlation between ELF values and binding energies calculated for co-crystals of 4-hydroxyphenylboronic acid (4HPBA) with four different aza donors using density functional theory with varying descriptions of dispersion. Boronic acids are gaining significant interest in the field of crystal engineering, but theoretical studies on their use in materials are still very limited. Here, we present a systematic investigation of the non-covalent interactions in experimentally realized co-crystals. Prior diffraction studies on these complexes have shown the competitive nature between the boronic acid functional group and the para-substituted phenolic group forming heteromeric interactions with aza donors. We determine the stability of the co-crystals by simulating their lattice energies, and the different dispersion descriptions show similar trends in lattice energies and lattice parameters. Our study bolsters the experimental observation of the boronic acid group as a competitive co-crystal former in addition to the well-studied phenolic group. Further research on correlating ELF values for physical binding could potentially transform this approach to a viable alternative for the computation of binding energies.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2023
Keywords
binding energy, co-crystals, dispersion corrected DFT, ELF, hydrogen-bonds, lattice energy
National Category
Condensed Matter Physics Theoretical Chemistry
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-101863 (URN)10.1088/1361-648X/acf638 (DOI)001068765700001 ()37659400 (PubMedID)2-s2.0-85171600035 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationThe Kempe Foundations
Note

Validerad;2023;Nivå 2;2023-10-31 (hanlid);

Licens full text: CC BY

Available from: 2023-10-31 Created: 2023-10-31 Last updated: 2023-10-31Bibliographically approved
Löfgren, R., Öberg, S. & Larsson, J. A. (2022). The diamond NV-center transition energies in the vicinity of an intrinsic stacking fault. AIP Advances, 12(3), Article ID 035009.
Open this publication in new window or tab >>The diamond NV-center transition energies in the vicinity of an intrinsic stacking fault
2022 (English)In: AIP Advances, E-ISSN 2158-3226, Vol. 12, no 3, article id 035009Article in journal (Refereed) Published
Abstract [en]

The negatively charged nitrogen vacancy (NV−) center in a diamond is a nanometer-sized defect with very sensitive properties that can be manipulated, for example, for single-molecule photoluminescence and nuclear magnetic resonance sensing, as a single photon source for quantum cryptography and as a qubit in room temperature quantum computing. To have a minimal perturbation of its properties, it is important to isolate the NV-center from other defects. One type of the extended defects that can be common in diamonds is the intrinsic stacking fault (ISF) associated with dislocations. In this work, we use density functional theory simulations to investigate how the distance between the NV− center and an ISF affects its properties, including the transition energies, spin density, and energy eigenvalues in the Kohn–Sham bandgap. We have found that the NV-center properties are only slightly perturbed when placed in the vicinity of an ISF. Even for an interdistance of only 3.8 Å between the NV-center and the ISF, the decrease in its zero phonon line (ZPL) energy is less than 6.8%. To more significantly perturb the ZPL, the NV-center has to be placed inside the stacking fault glide plane (11.3% decrease). The changes in ZPL are in the majority of cases lower than the bulk value, which can be used to guide experimental observations. We find that the NV-center is only weakly interacting with ISFs, which in addition to a small bulk conversion depth of 5 Å to a diamond surface is important for their technological use.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2022
National Category
Metallurgy and Metallic Materials Condensed Matter Physics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-89902 (URN)10.1063/5.0080096 (DOI)000772898200003 ()2-s2.0-85126222852 (Scopus ID)
Funder
Swedish Research Council, 621-2012- 3999Carl Tryggers foundation , 13-243Carl Tryggers foundation , 14-269Knut and Alice Wallenberg FoundationThe Kempe Foundations
Note

Validerad;2022;Nivå 2;2022-03-30 (hanlid)

Available from: 2022-03-30 Created: 2022-03-30 Last updated: 2023-09-05Bibliographically approved
Löfgren, R., Öberg, S. & Larsson, J. A. (2020). A theoretical study of de-charging excitations of the NV-center in diamond involving a nitrogen donor. New Journal of Physics, 22(12), Article ID 123042.
Open this publication in new window or tab >>A theoretical study of de-charging excitations of the NV-center in diamond involving a nitrogen donor
2020 (English)In: New Journal of Physics, E-ISSN 1367-2630, Vol. 22, no 12, article id 123042Article in journal (Refereed) Published
Abstract [en]

The negatively charged nitrogen vacancy centre in diamond is a promising candidate for future nanoscale quantum applications. For its operation it is important to have control of the centres charge state, and to avoid temporary disappearance of the NV-center's functionality, termed photo-blinking. In this work, we use density functional theory simulations to investigate excitations that result in loss of an electron from NV to a nearby nitrogen donor (donor-N+), leading to NV0 and donor-N0 charge state, and the corresponding deexcitation. Since these processes involve two different localized defect centres in the diamond lattice (the NV-center and the donor-N) they are non-local excitations. We have studied the de-charging both as a one-photon process and through a sequential two-photon process via the NV-center excited state. We propose de-charging directly from the NV-center to the donor-N as a possible mechanism for photo-blinking of the NV-center that involve an additional electron spin resonance active defect, the donor-N0. We have found that the excitation energies are converged when the distance between the two is larger than 10.4 Å. We also compute excitations to the conduction band edge from NV (to NV0) and from donor-N0 (to donor-N+) using G0W0 + BSE.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2020
Keywords
DFT, NV-center, diamond, ab initio, GW + BSE, electron donor, nitrogen
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-81958 (URN)10.1088/1367-2630/abd1ae (DOI)000604774300001 ()2-s2.0-85099362613 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationThe Kempe FoundationsSwedish Research Council, 621-2012-3999, 2018-05973Carl Tryggers foundation
Note

Validerad;2021;Nivå 2;2021-01-21 (alebob)

Available from: 2020-12-11 Created: 2020-12-11 Last updated: 2024-01-17Bibliographically approved
Bathen, M. E., Coutinho, J., Ayedh, H. M., Hassan, J. U., Farkas, I., Öberg, S., . . . Vines, L. (2019). Anisotropic and plane-selective migration of the carbon vacancy in SiC: Theory and experiment. Physical Review B, 100(1), Article ID 014103.
Open this publication in new window or tab >>Anisotropic and plane-selective migration of the carbon vacancy in SiC: Theory and experiment
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2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 1, article id 014103Article in journal (Refereed) Published
Abstract [en]

We investigate the migration mechanism of the carbon vacancy (VC) in silicon carbide (SiC) using a combination of theoretical and experimental methodologies. The VC, commonly present even in state-of-the-art epitaxial SiC material, is known to be a carrier lifetime killer and therefore strongly detrimental to device performance. The desire for VC removal has prompted extensive investigations involving its stability and reactivity. Despite suggestions from theory that VC migrates exclusively on the C sublattice via vacancy-atom exchange, experimental support for such a picture is still unavailable. Moreover, the existence of two inequivalent locations for the vacancy in 4H-SiC [hexagonal, VC(h), and pseudocubic, VC(k)] and their consequences for VC migration have not been considered so far. The first part of the paper presents a theoretical study of VC migration in 3C- and 4H-SiC. We employ a combination of nudged elastic band (NEB) and dimer methods to identify the migration mechanisms, transition state geometries, and respective energy barriers for VC migration. In 3C-SiC, VC is found to migrate with an activation energy of EA=4.0 eV. In 4H-SiC, on the other hand, we anticipate that VC migration is both anisotropic and basal-plane selective. The consequence of these effects is a slower diffusivity along the axial direction, with a predicted activation energy of EA=4.2 eV, and a striking preference for basal migration within the h plane with a barrier of EA=3.7 eV, to the detriment of the k-basal plane. Both effects are rationalized in terms of coordination and bond angle changes near the transition state. In the second part, we provide experimental data that corroborates the above theoretical picture. Anisotropic migration of VC in 4H-SiC is demonstrated by deep level transient spectroscopy (DLTS) depth profiling of the Z1/2 electron trap in annealed samples that were subject to ion implantation. Activation energies of EA=(4.4±0.3) eV and EA=(3.6±0.3) eV were found for VC migration along the c and a directions, respectively, in excellent agreement with the analogous theoretical values. The corresponding prefactors of D0=0.54cm2/s and 0.017cm2/s are in line with a simple jump process, as expected for a primary vacancy point defect.

Place, publisher, year, edition, pages
American Physical Society, 2019
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-75557 (URN)10.1103/PhysRevB.100.014103 (DOI)000474364500002 ()2-s2.0-85070111566 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-08-16 (johcin)

Available from: 2019-08-16 Created: 2019-08-16 Last updated: 2019-08-16Bibliographically approved
Löfgren, R., Pawar, R., Öberg, S. & Larsson, A. (2019). The bulk conversion depth of the NV-center in diamond: computing a charged defect in a neutral slab. New Journal of Physics, 21, Article ID 053037.
Open this publication in new window or tab >>The bulk conversion depth of the NV-center in diamond: computing a charged defect in a neutral slab
2019 (English)In: New Journal of Physics, E-ISSN 1367-2630, Vol. 21, article id 053037Article in journal (Refereed) Published
Abstract [en]

The negatively charged nitrogen vacancy (NV-) center in diamond has properties that make it a promising candidate for applications such as a qubit in room temperature quantum computing, single-molecule photoluminescence and NMR sensor, and as a single photon source for quantum cryptography. For many of its uses it is desirable to have the NV-center close to the diamond surface. In this work, we use density functional theory simulations to investigate how the distance of the NV- center to a surface, and its orientation, affect its properties, including the zero-phonon-line. We study the three technologically important surfaces terminated with fluorine, oxygen/hydroxyl and nitrogen. Since the NV-center is charged it requires special measures to simulate within a slab-model. We use the recently proposed charging with a substitutional donor in the diamond lattice resulting in a neutral super-cell, which provides very satisfactory results. We have found that the NV-centers properties converge to bulk values already at 5 angstrom depth.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2019
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-74898 (URN)10.1088/1367-2630/ab1ec5 (DOI)000469973900007 ()2-s2.0-85069479116 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-06-24 (johcin)

Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2024-01-17Bibliographically approved
Allali, N., Urbanova, V., Etienne, M., Devaux, X., Mallet, M., Vigolo, B., . . . Mamane, V. (2018). Accurate control of the covalent functionalization of single-walled carbon nanotubes for the electro-enzymatically controlled oxidation of biomolecules. Beilstein Journal of Nanotechnology, 9, 2750-2762
Open this publication in new window or tab >>Accurate control of the covalent functionalization of single-walled carbon nanotubes for the electro-enzymatically controlled oxidation of biomolecules
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2018 (English)In: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 9, p. 2750-2762Article in journal (Refereed) Published
Abstract [en]

Single-walled carbon nanotubes (SWCNTs) were functionalized by ferrocene through ethyleneglycol chains of different lengths (FcETGn) and the functionalized SWCNTs (f-SWCNTs) were characterized by different complementary analytical techniques. In particular, high-resolution scanning electron transmission microscopy (HRSTEM) and electron energy loss spectroscopy (EELS) analyses support that the outer tubes of the carbon-nanotube bundles were covalently grafted with FcETGn groups. This result confirms that the electrocatalytic effect observed during the oxidation of the reduced form of nicotinamide adenine dinucleotide (NADH) co-factor by the f-SWCNTs is due to the presence of grafted ferrocene derivatives playing the role of a mediator. This work clearly proves that residual impurities present in our SWCNT sample (below 5 wt. %) play no role in the electrocatalytic oxidation of NADH. Moreover, molecular dynamic simulations confirm the essential role of the PEG linker in the efficiency of the bioelectrochemical device in water, due to the favorable interaction between the ETG units and water molecules that prevents π-stacking of the ferrocene unit on the surface of the CNTs. This system can be applied to biosensing, as exemplified for glucose detection. The well-controlled and well-characterized functionalization of essentially clean SWCNTs enabled us to establish the maximum level of impurity content, below which the f-SWCNT intrinsic electrochemical activity is not jeopardized.

Place, publisher, year, edition, pages
Beilstein-Institut, 2018
Keywords
biosensing, carbon nanotubes, covalent functionalization, electrocatalysis, ferrocene
National Category
Other Physics Topics
Research subject
Experimental Physics; Applied Physics
Identifiers
urn:nbn:se:ltu:diva-71587 (URN)10.3762/bjnano.9.257 (DOI)000448782500001 ()30416926 (PubMedID)2-s2.0-85056284634 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-11-15 (johcin)

Available from: 2018-11-15 Created: 2018-11-15 Last updated: 2023-10-28Bibliographically approved
Berezovsky, V. & Öberg, S. (2018). Computational study of the CO adsorption and diffusion in zeolites: validating the Reed–Ehrlich model. Adsorption, 24(4), 403-413
Open this publication in new window or tab >>Computational study of the CO adsorption and diffusion in zeolites: validating the Reed–Ehrlich model
2018 (English)In: Adsorption, ISSN 0929-5607, E-ISSN 1572-8757, Vol. 24, no 4, p. 403-413Article in journal (Refereed) Published
Abstract [en]

Molecular simulations have been employed to explore at the microscopic scale the adsorption of CO in zeolites (MFI, CHA and DDR). On the basis of classical force fields, grand canonical Monte Carlo simulations are performed to predict the adsorption properties (isotherms) of these types of zeolites up to high pressure. Subsequent careful analysis yields details the microscopic mechanism in play, along the whole adsorption process, together with a considering of the arrangements of CO in MFI at high pressure. This work also summarizes an approach which uses single component diffusion data in prediction of multicomponent diffusion.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Condensed Matter Physics Physical Chemistry Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-68541 (URN)10.1007/s10450-018-9948-z (DOI)000432610800006 ()2-s2.0-85046018279 (Scopus ID)
Funder
Swedish National Infrastructure for Computing (SNIC)Swedish Foundation for Strategic Research
Note

Validerad;2018;Nivå 2;2018-08-07 (rokbeg)

Available from: 2018-04-28 Created: 2018-04-28 Last updated: 2019-01-18Bibliographically approved
Santos, P., Coutinho, J. & Öberg, S. (2018). First-principles calculations of iron-hydrogen reactions in silicon. Journal of Applied Physics, 123(24), Article ID 245703.
Open this publication in new window or tab >>First-principles calculations of iron-hydrogen reactions in silicon
2018 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 123, no 24, article id 245703Article in journal (Refereed) Published
Abstract [en]

Controlling the contamination of silicon materials by iron, especially dissolved interstitial iron (Fe-i), is a longstanding problem with recent developments and several open issues. Among these, we have the question whether hydrogen can assist iron diffusion or if significant amounts of substitutional iron (Fe-s) can be created. Using density functional calculations, we explore the structure, formation energies, binding energies, migration, and electronic levels of several FeH complexes in Si. We find that a weakly bound FeiH pair has a migration barrier close to that of isolated Fe-i and a donor level at E-v + 0.5 eV. Conversely, FeiH2 (0/+) is estimated at E-v + 0.33 eV. These findings suggest that the hole trap at E-v + 0.32 eV obtained by capacitance measurements should be assigned to FeiH2 . FesH-related complexes show only deep acceptor activity and are expected to have little effect on minority carrier life-time in p-type Si. The opposite conclusion can be drawn for n-type Si. We find that while in H-free material Fe i defects have lower formation energy than Fe-s , in hydrogenated samples Fe-s -related defects become considerably more stable. This would explain the observation of an electron paramagnetic resonance signal attributed to a FesH-related complex in hydrogenated Si, which was quenched from above 1000 degrees C to iced-water temperature.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2018
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-70160 (URN)10.1063/1.5039647 (DOI)000437034500044 ()2-s2.0-85049239103 (Scopus ID)
Note

Validerad;2018;Nivå 2; 2018-07-25 (inah)

Available from: 2018-07-25 Created: 2018-07-25 Last updated: 2018-08-08Bibliographically approved
Avakyan, L., Paramonova, E., Coutinho, J., Öberg, S., Bystrov, V. & Bugaev, L. (2018). Optoelectronics and defect levels in hydroxyapatite by first-principles. Journal of Chemical Physics, 148(15), Article ID 154706.
Open this publication in new window or tab >>Optoelectronics and defect levels in hydroxyapatite by first-principles
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2018 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 148, no 15, article id 154706Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2018
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-68499 (URN)10.1063/1.5025329 (DOI)000430485700016 ()29679976 (PubMedID)2-s2.0-85045830684 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-04-26 (svasva)

Available from: 2018-04-25 Created: 2018-04-25 Last updated: 2021-10-15Bibliographically approved
Wright, E., Coutinho, J., Öberg, S. & Torres, V. (2017). A first-principles model of copper-boron interactions in Si: for the light-induced degradation of solar Si. Journal of Physics: Condensed Matter, 29(6), Article ID 065701.
Open this publication in new window or tab >>A first-principles model of copper-boron interactions in Si: for the light-induced degradation of solar Si
2017 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, no 6, article id 065701Article in journal (Refereed) Published
Abstract [en]

The recent discovery that Cu contamination of Si combined with light exposure has a significant detrimental impact on carrier life-time has drawn much concern within the solar-Si community. The effect, known as the copper-related light-induced degradation (Cu-LID) of Si solar cells, has been connected to the release of Cu interstitials within the bulk (2016 Sol. Energy Mater. Sol. Cells 147 115-26). In this paper, we describe a comprehensive analysis of the formation/dissociation process of the CuB pair in Si by means of first-principles modelling, as well as the interaction of CuB defects with photo-excited minority carriers. We confirm that the long-range interaction between the Cu-i(+) cation and the B-s(-) anion has a Coulomb-like behaviour, in line with the trapping-limited diffusivity of Cu observed by transient ion drift measurements. On the other hand, the short-range interaction between the d-electrons of Cu and the excess of negative charge on B-s(-) produces a repulsive effect, thereby decreasing the binding energy of the pair when compared to the ideal point-charge Coulomb model. We also find that metastable CuB pairs produce acceptor states just below the conduction band minimum, which arise from the Cu level emptied by the B acceptor. Based on these results, we argue that photo-generated minority carriers trapped by the metastable pairs can switch off the Coulomb interaction that holds the pairs together, enhancing the release of Cu interstitials, and acting as a catalyst for Cu-LID.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2017
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-61817 (URN)10.1088/1361-648X/aa4d78 (DOI)000391564700001 ()27991421 (PubMedID)2-s2.0-85011968739 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-02-03 (andbra)

Available from: 2017-02-03 Created: 2017-02-03 Last updated: 2021-03-11Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0292-1159

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