Date: Sep. 22 (Fri.), 2023
Time: 16:00-17:00
Place: On Zoom and Seminar Room A615 , ISSP(Hybrid)
Speaker:
Taisuke OzakiAffiliation: ISSP, the Univ. of Tokyo
Title :
Closest Wannier functions to a given set of localized orbitals
Abstract:
Wannier functions (WFs) play a pivotal role in analyzing the electronic structures of
real materials and in furthering electronic structure methods, alongside
density functional theory (DFT) and other electronic structure theories [1]. In
this talk, I will present a novel method to calculate the closest Wannier
functions (CWFs) to a given set of localized guiding functions, such as atomic
orbitals, hybrid atomic orbitals, and molecular orbitals, based on minimization
of a distance measure function [2]. It is shown that the minimization is
directly achieved by a polar decomposition [3] of a projection matrix via
singular value decomposition, making iterative calculations and complications
arising from the choice of the gauge irrelevant. The disentanglement of bands
is inherently addressed by introducing a smoothly varying window function and a
greater number of Bloch functions, even for isolated bands. In addition to
atomic and hybrid atomic orbitals, we introduce embedded molecular orbitals in
molecules and bulks as guiding functions, and demonstrate that the Wannier
interpolated bands accurately reproduce the targeted conventional bands of a
wide variety of systems including Si, Cu, the TTF-TCNQ molecular crystal, and a
topological insulator of Bi2Se3 [4]. We further show the
usefulness of the proposed method in calculating effective atomic charges.
These numerical results not only establish our proposed method as an efficient
alternative for calculating WFs, but also suggest that the concept of CWF can
serve as a foundation for developing novel methods to analyze electronic
structures and calculate physical properties.
[1] N. Marzari and D. Vanderbilt, Phys. Rev. B 56,12847 (1997).
[2] T. Ozaki, arXiv:2306.15296.
[3] K. Fan and A. J. Hoffman, Proc. Amer. Math. Soc. 6, 111 (1955).
[4] https://www.openmx-square.org/cwf/
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Once you make a registration below, you will get the access information of Zoom by e-mail.
Contact : Taisuke Ozaki ( t-ozaki@issp.u-tokyo.ac.jp )