Efficient on-the-fly interpolation technique for Bethe-Salpeter calculations of optical spectra
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- 作者：Yannick Gillet ; yannick.gillet@uclouvain.be" class="auth_mail" title="E-mail the corresponding author ; Matteo Giantomassi ; Xavier Gonze
- 关键词：Bethe&ndash ; Salpeter Equation ; Lanczos algorithm
- 刊名：Computer Physics Communications
- 出版年：2016
- 出版时间：June 2016
- 年：2016
- 卷：203
- 期：Complete
- 页码：83-93
- 全文大小：801 K
文摘
The Bethe–Salpeter formalism represents the most accurate method available nowadays for computing neutral excitation energies and optical spectra of crystalline systems from first principles. Bethe–Salpeter calculations yield very good agreement with experiment but are notoriously difficult to converge with respect to the sampling of the electronic wavevectors. Well-converged spectra therefore require significant computational and memory resources, even by today’s standards. These bottlenecks hinder the investigation of systems of great technological interest. They are also barriers to the study of derived quantities like piezoreflectance, thermoreflectance or resonant Raman intensities.
We present a new methodology that decreases the workload needed to reach a given accuracy. It is based on a double-grid on-the-fly interpolation within the Brillouin zone, combined with the Lanczos algorithm. It achieves significant speed-up and reduction of memory requirements. The technique is benchmarked in terms of accuracy on silicon, gallium arsenide and lithium fluoride. The scaling of the performance of the method as a function of the Brillouin Zone point density is much better than a conventional implementation. We also compare our method with other similar techniques proposed in the literature.