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O: Fachverband Oberflächenphysik

O 10: Focus Session: Frontiers of Electronic-Structure Theory – Advances in Time-Dependent and Nonequilibrium Ab Initio Methods II

O 10.9: Talk

Monday, March 18, 2024, 17:00–17:15, HE 101

Brillouin zone sampling in ONETEP — •Chengcheng Xiao, Peter Haynes, and Arash Mostofi — Departments of Materials and Physics, and the Thomas Young Centre for Theory and Simulation of Materials, Imperial College London, London SW7 2AZ, United Kingdom

ONETEP is a linear-scaling density functional theory (DFT) program with large basis set (plane-wave) accuracy on parallel computers. ONETEP was originally designed to study large-scale systems, including macromolecules and nanocrystals. Because of this, ONETEP is restricted to Gamma-point only for self-consistent calculations. However, many systems of interest are periodic at short-scales in one or two dimensions, e.g., nanowires and surfaces. In such cases, significant computational efficiency can be achieved via dense sampling of the Brillouin zone (rather than creating large supercells).

Here, we introduce two types of Brillouin zone sampling methods in ONETEP. The first is targeted at small periodic systems and exploits the fact that the localization constraints of the non-orthogonal Wannier functions (NGWFs) can be lifted. The second keeps the NGWFs localized and the k-dependence is introduced as phase factors to the Hamiltonian matrix elements (similar to the tight-binding method). This method keeps the code linear scaling with k-points and is aimed at intermediate-sized systems.

These developments extend the operability of ONETEP to short- and intermediate-scale periodic systems, including 2D materials, nanowires, nanotubes, surfaces, and interfaces.

Keywords: ONETEP; Brillouin zone sampling