SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 30: 2D Materials I: Electronic Structure

O 30.7: Vortrag

Dienstag, 28. März 2023, 12:00–12:15, GER 37

Limitations of supercell extrapolation for charged defects at surfaces & 2D materials — •Christoph Freysoldt¹, Anne Marie Z. Tan^2,3, Richard G. Hennig², and Jörg Neugebauer¹ — ¹Max-Planck-Institut für Eisenforschung, Max-Planck-Straße 1, 40237 Düsseldorf, Germany — ²Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA — ³School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore

Ab initio calculations of defects often employ the repeated slab approach for its simplicity. Unfortunately, spurious interactions between the defect and its periodic images make it sometimes challenging to estimate the dilute limit, that is relevant for comparison to experiment, from computationally affordable system sizes. A simple and seemingly straightforward approach is to extrapolate from a series of finite supercell sizes to the infinite-size limit, assuming a smooth, polynomial dependence of the energy on inverse supercell size. By means of explicit density-functional theory supercell calculations and simplified electrostatic models we demonstrate that the dependence of the formation energy on supercell size can be more complex than is commonly assumed. We show that this complexity cannot be captured by the simple extrapolation approaches. In contrast, suitable correction schemes are shown to provide rapidly converging results even for 2D materials.

[1] C. Freysoldt, J. Neugebauer, A. M. Z. Tan, R. G. Hennig, Phys. Rev. B 105, 014103 (2022).