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TYC Symposium: Georg Kresse – Vienna, Volker Blum – Duke & Chris Skylaris – Soton

2 July 2024 @ 3:00 pm 6:00 pm

XLG1 LT, Christopher Ingold Building, followed by a drinks reception in the Nyholm Room

Machine learning and beyond DTF methods: quantative materials modelling at your fingertips (title to be confirmed) – Georg Kresse, University of Vienna

Energy Levels, Their Spin Character, Symmetry, Defects and Dopants: Organic-Inorganic Semiconductors from Large-Scale Hybrid DFT – Volker Blum, Duke University
Hybrid organic-inorganic metal halide perovskites (HOI-MHPs) have captured the attention of a large audience since several three-dimensional perovskites emerged as leading candidates for next-generation photovoltaics. The ability to tailor hybrid organic-inorganic perovskites of different dimensionalities (especially layered, i.e., two-dimensional) by rationally selecting organic and inorganic functionalities renders them interesting for practically any semiconductor functionality, including coherent phenomena, spin transport and spin-optoelectronic phenomena. We show how layered HOI-MHPs can be understood as effective quantum wells, with relative band alignments captured accurately by spin-orbit-coupled hybrid density functional theory for large systems, here applied to systems up to 3,383 atoms in size. Deliberate introduction of inversion symmetry breaking by chiral molecules leads to large relativistic spin splittings that can be rationalized and tuned using a simple structural descriptor in the inorganic layer. Based on this understanding, we show how tunable structural chirality transfer occurs in tailored layered HOI-MHPs as well as quantum dots. One key challenge for HOI-MHPs is dopability, i.e., deliberate control over carrier type (n-type or p-type) and carrier concentrations by substitutions. In supercell calculations including over 1,500 atoms, we directly predict doping levels of Bi and Sn in the paradigmatic layered perovskite phenethylammonium lead iodide, showing that these results in principle agree well with experimental observations. In particular, we explain the observed slight p-type doping by Sn substitution of Pb via a preference of Pb vacancies to occur in close proximity to substitutional Sn. A detailed analysis of experimental data shows that Bi-doping, which should lead to n-type doping, appears to be compensated by a defect population with lower-lying acceptor levels, which must be identified and mitigated in order to achieve successful doping.

Large-scale quantum atomistic and multiscale simulations of batteriesChris-Kriton Skylaris, University of Southampton
We are developing new software tools with unique capabilities for large-scale atomistic electrochemical simulations under operational conditions. The aim is to not only capture all the essential chemistry and physics of devices such as batteries, but also to provide the parameters needed for bridging atomistic with larger scale simulations. Our developments are within the ONETEP program [1], which is based on a linear-scaling reformulation of density functional theory (DFT) that allows atomistic simulations of several orders of magnitude more atoms than conventional DFT approaches, so that we can study more complex models. In this talk, I will outline our developments so far, which include methods for metallic systems, solvent and electrolyte models [2], and a grand-canonical approach which allows simulations at fixed voltage with respect to a computational reference electrode [3-4]. Also, I will describe our ongoing development of new DFTB approaches within the linear-scaling framework of ONETEP which will enable simulations at longer timescales to allow study of problems such as the chemistry taking place during SEI formation. Finally, I will summarise recent applications of these tools to the process of lithium metal deposition on anodes and its competition with Li dendrite formation [5], one of the major mechanisms of battery degradation.


[1] The ONETEP linear-scaling density functional theory program. J. C. A. Prentice, J. Aarons, J. C. Womack, A. E. A. Allen, L. Andrinopoulos, L. Anton, R. A. Bell, A. Bhandari, G. A. Bramley, R. J. Charlton, R. J. Clements, D. J. Cole, G. Constantinescu, F. Corsetti, S. M.-M. Dubois, K. K. B. Duff, J. M. Escartín, A. Greco, Q. Hill, L. P. Lee, E. Linscott, D. D. O’Regan, M. J. S. Phipps, L. E. Ratcliff, Á. R. Serrano, E. W. Tait, G. Teobaldi, V. Vitale, N. Yeung, T. J. Zuehlsdorff, J. Dziedzic, P. D. Haynes, N. D. M. Hine, A. A. Mostofi, M. C. Payne, and C.-K. Skylaris. J. Chem. Phys. 152 (2020) 174111.
[2] Practical Approach to Large-Scale Electronic Structure Calculations in Electrolyte Solutions via Continuum-Embedded Linear-Scaling Density Functional Theory. J. Dziedzic, A. Bhandari, L. Anton, C. Peng, J. C. Womack, M. Famili, D. Kramer, and C.-K. Skylaris. J. Phys. Chem. C. 124 (2020) 7860-7872.
[3] Electronic structure calculations in electrolyte solutions: Methods for neutralization of extended charged interfaces. A. Bhandari, L. Anton, J. Dziedzic, C. Peng, D. Kramer, and C.-K. Skylaris. J. Chem. Phys. 153 (2020) 124101.
[4] Electrochemistry from first-principles in the grand canonical ensemble. A. Bhandari, C. Peng, J. Dziedzic, L. Anton, J. R. Owen, D. Kramer, and C.-K. Skylaris. J. Chem. Phys 155 (2021) 024114.
[5] Mechanism of Li nucleation at graphite anodes and mitigation strategies. C. Peng, A. Bhandari, J. Dziedzic, J. R. Owen, C.-K. Skylaris, and D. Kramer.  J. Mater. Chem. A, 2021,9, 16798; Li nucleation on the graphite anode under potential control in Li-ion batteries. A. Bhandari, C. Peng, J. Dziedzic, J.R. Owen, D. Kramer, C.-K. Skylaris, J. Mater. Chem. A, 2022,10, 11426.

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