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Publications (10 of 59) Show all publications
Krishna, A., Wadbro, E., Kholer, C., Mitev, P. D., Broqvist, P. & Kullgren, J. (2019). A material chemistry tool for generating two body potentials. In: : . Paper presented at Swedish eScience Academy.
Open this publication in new window or tab >>A material chemistry tool for generating two body potentials
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2019 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-396395 (URN)
Conference
Swedish eScience Academy
Available from: 2019-11-04 Created: 2019-11-04 Last updated: 2019-11-04
Kettner, M., Duchon, T., Wolf, M. J., Kullgren, J., Senanayake, S. D., Hermansson, K., . . . Nehasil, V. (2019). Anion-mediated electronic effects in reducible oxides: Tuning the valence band of ceria via fluorine doping. Journal of Chemical Physics, 151(4), Article ID 044701.
Open this publication in new window or tab >>Anion-mediated electronic effects in reducible oxides: Tuning the valence band of ceria via fluorine doping
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2019 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 151, no 4, article id 044701Article in journal (Refereed) Published
Abstract [en]

Combining experimental spectroscopy and hybrid density functional theory calculations, we show that the incorporation of fluoride ions into a prototypical reducible oxide surface, namely, ceria(111), can induce a variety of nontrivial changes to the local electronic structure, beyond the expected increase in the number of Ce3+ ions. Our resonant photoemission spectroscopy results reveal new states above, within, and below the valence band, which are unique to the presence of fluoride ions at the surface. With the help of hybrid density functional calculations, we show that the different states arise from fluoride ions in different atomic layers in the near surface region. In particular, we identify a structure in which a fluoride ion substitutes for an oxygen ion at the surface, with a second fluoride ion on top of a surface Ce4+ ion giving rise to F 2p states which overlap the top of the O 2p band. The nature of this adsorbate F--Ce4+ resonant enhancement feature suggests that this bond is at least partially covalent. Our results demonstrate the versatility of anion doping as a potential means of tuning the valence band electronic structure of ceria.

National Category
Theoretical Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-393127 (URN)10.1063/1.5109955 (DOI)000478625700040 ()31370552 (PubMedID)
Funder
Swedish Research CouncileSSENCE - An eScience Collaboration
Note

M. Kettner, T. Duchoň, and M. J. Wolf contributed equally to this work.

Available from: 2019-09-24 Created: 2019-09-24 Last updated: 2019-09-24Bibliographically approved
Castleton, C. W. M., Lee, A. & Kullgren, J. (2019). Benchmarking Density Functional Theory Functionals for Polarons in Oxides: Properties of CeO2. The Journal of Physical Chemistry C, 123(9), 5164-5175
Open this publication in new window or tab >>Benchmarking Density Functional Theory Functionals for Polarons in Oxides: Properties of CeO2
2019 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 9, p. 5164-5175Article in journal (Refereed) Published
Abstract [en]

We examine methods for studying polarons in metal oxides with density functional theory (DFT), using the example of cerium dioxide and the functionals, local density approximation + U (LDA+U), generalized gradient approximation + U (GGA+U) in the Perdew-Burke-Ernzerhof parametrization (PBE+U), as well as the hybrid functionals B3LYP, Heyd Scuseria Ernzerhof (HSE)03, HSE06, and PBEO. We contrast the four polaron energies commonly reported in different parts of the literature: formation energy, localization/relaxation energy, density-of-states level, and polaron-hopping activation barrier. Qualitatively, all these functionals predict "small" (Holstein) polarons on the scale of a single lattice site, although LDA +U and GGA+U are more effective than the hybrids at localizing the Ce 4f electrons. The improvements over pure LDA/GGA appear because of changes in the filled Ce 4f states when using LDA/GGA+U but due to changes in the empty Ce 4f states when using the hybrids. DFT is shown to have sufficient correlation to predict both adiabatic and (approximate) diabatic hopping barriers. Overall, LDA+U = 6 eV provides the best description in comparison to the experiment, followed by GGA+U = 5 eV. The hybrids are worse, tending to overestimate the gap and significantly underestimate the polaron-hopping barriers.

National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-380460 (URN)10.1021/acs.jpcc.8b09134 (DOI)000460996000002 ()
Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2019-03-28Bibliographically approved
Broqvist, P., Kullgren, J., Zhang, C., Mitev, P. D. & Hermansson, K. (2019). Chemistry of Complex Materials. In: : . Paper presented at Swedish eScience Academy.
Open this publication in new window or tab >>Chemistry of Complex Materials
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2019 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-395887 (URN)
Conference
Swedish eScience Academy
Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-10-25
Kocmaruk, B., Kullgren, J. & Broqvist, P. (2019). Computational modelling of nanosystems. In: : . Paper presented at 4th PhD Chemistry Miniconference.
Open this publication in new window or tab >>Computational modelling of nanosystems
2019 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-395936 (URN)
Conference
4th PhD Chemistry Miniconference
Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-10-25
Kocmaruk, B., Kullgren, J. & Broqvist, P. (2019). Computational modelling of nanosystems. In: : . Paper presented at Swedish eScience Academy.
Open this publication in new window or tab >>Computational modelling of nanosystems
2019 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-395889 (URN)
Conference
Swedish eScience Academy
Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-10-25
Källquist, I., Naylor, A. J., Baur, C., Chable, J., Kullgren, J., Fichtner, M., . . . Hahlin, M. (2019). Degradation Mechanisms in Li2VO2F Li-Rich Disordered Rock-Salt Cathodes. Chemistry of Materials, 31(16), 6084-6096
Open this publication in new window or tab >>Degradation Mechanisms in Li2VO2F Li-Rich Disordered Rock-Salt Cathodes
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2019 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 16, p. 6084-6096Article in journal (Refereed) Published
Abstract [en]

The increased energy density in Li-ion batteries is particularly dependent on the cathode materials that so far have been limiting the overall battery performance. A new class of materials, Li-rich disordered rock salts, has recently been brought forward as promising candidates for next-generation cathodes because of their ability to reversibly cycle more than one Li-ion per transition metal. Several variants of these Li-rich cathode materials have been developed recently and show promising initial capacities, but challenges concerning capacity fade and voltage decay during cycling are yet to be overcome. Mechanisms behind the significant capacity fade of some materials must be understood to allow for the design of new materials in which detrimental reactions can be mitigated. In this study, the origin of the capacity fade in the Li-rich material Li2VO2F is investigated, and it is shown to begin with degradation of the particle surface that spreads inward with continued cycling.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-394265 (URN)10.1021/acs.chemmater.9b00829 (DOI)000483435400005 ()
Funder
Swedish Research Council, 2016-03545EU, Horizon 2020, 711792EU, Horizon 2020, 730872StandUpSwedish National Infrastructure for Computing (SNIC)
Available from: 2019-10-09 Created: 2019-10-09 Last updated: 2019-10-09Bibliographically approved
Du, D., Kullgren, J., Hermansson, K. & Broqvist, P. (2019). From Ceria Clusters to Nanoparticles: Superoxides and Supercharging. The Journal of Physical Chemistry C, 123(3), 1742-1750
Open this publication in new window or tab >>From Ceria Clusters to Nanoparticles: Superoxides and Supercharging
2019 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 3, p. 1742-1750Article in journal (Refereed) Published
Abstract [en]

Several studies have reported a dramatically increased oxygen storage capacity (OSC) for small ceria nanoparticles (∼5 nm). Both experiments and theory have correlated this effect with superoxide ion formation. In previous studies, density functional theory (DFT) calculations with the PBE+U density functional have been used, and the obtained results were only in qualitative agreement with the experimental observations. One severe problem is the underbinding of the O2 molecule upon superoxide ion formation, which suggests that such species should not exist above room temperature. In this work, we use hybrid DFT functional to resolve this problem. We find that the discrepancy between theory and experiment originates from an incorrect estimate of the energy associated with the localized f-electrons with respect to the oxygen p-levels. By using average O2 adsorption energies from hybrid DFT calculations, extrapolated to large nanoparticles (3−10 nm), in conjunction with first-order desorption kinetics, we find that superoxide ions are indeed stable on nanosized ceria well above room temperature, in accordance with experiments.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-377356 (URN)10.1021/acs.jpcc.8b08977 (DOI)000457067500025 ()
Funder
Swedish Research CouncilÅForsk (Ångpanneföreningen's Foundation for Research and Development)eSSENCE - An eScience Collaboration
Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-04-24Bibliographically approved
Mirsakiyeva, A., Ebadi, M., Araujo, C. M., Brandell, D., Broqvist, P. & Kullgren, J. (2019). Initial Steps in PEO Decomposition on a Li Metal Electrode. The Journal of Physical Chemistry C, 123(37), 22851-22857
Open this publication in new window or tab >>Initial Steps in PEO Decomposition on a Li Metal Electrode
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2019 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 37, p. 22851-22857Article in journal (Refereed) Published
Abstract [en]

Poly(ethylene oxide) (PEO) is the most widely used compound as a solid-state (solvent-free) polymer electrolyte for Li batteries, mainly due to its low glass transition temperature (T-g) and ability to dissolve Li salts. It is also frequently suggested that its cathodic stability renders it possible to operate with Li metal anodes in the design of high energy density storage devices. However, little is still known about the true interfacial chemistry between Li metal and PEO and how these two materials interact with each other. We are here exploring this relationship by the means of density functional theory (DFT)-based modeling. Using bulk structures and isolated PEO chains, we have found that there is a strong thermodynamic driving force to oxidize Li metal into lithium oxide (Li2O) when PEO is decomposed into C2H4 and H-2, irrespectively of the PEO oligomer length. Explicit modeling of PEO on a Li(100) surface reveals that all steps in the decomposition are exothermic and that the PEO/Li metal system should have a layer of Li2O between the polymer electrolyte and the metal surface. These insights and the computational strategy adopted here could be highly useful to better tailor polymer electrolytes with favorable interfacial properties.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-395686 (URN)10.1021/acs.jpcc.9b07712 (DOI)000487349600017 ()
Funder
StandUpSwedish Energy Agency, 39036-1eSSENCE - An eScience CollaborationÅForsk (Ångpanneföreningen's Foundation for Research and Development)
Available from: 2019-10-24 Created: 2019-10-24 Last updated: 2019-10-24Bibliographically approved
Meier de Andrade, A., Kullgren, J., Sá, J. & Broqvist, P. (2019). Insights into reactive nanoparticles. In: : . Paper presented at 2019 EMMC-eSSENCE Meeting "Multiscale modelling of materials and molecules: Physics-based and data-driven.".
Open this publication in new window or tab >>Insights into reactive nanoparticles
2019 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-394007 (URN)
Conference
2019 EMMC-eSSENCE Meeting "Multiscale modelling of materials and molecules: Physics-based and data-driven."
Available from: 2019-10-01 Created: 2019-10-01 Last updated: 2019-10-01
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3570-0050

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