Speeding up the solution of the Bethe-Salpeter equation by a double-grid method and Wannier interpolation

摘要

The Bethe-Salpeter equation is a widely used approach to describe opticalexcitations in bulk semiconductors. It leads to spectra that are in very goodagreement with experiment, but the price to pay for such accuracy is a veryhigh computational burden. One of the main bottlenecks is the large number ofk-points required to obtain converged spectra. In order to circumvent thisproblem we propose a strategy to solve the Bethe-Salpeter equation based on adouble-grid technique coupled to a Wannier interpolation of the Kohn-Sham bandstructure. This strategy is then benchmarked for a particularly difficult case,the calculation of the absorption spectrum of GaAs, and for the well studiedcase of Si. The considerable gains observed in these cases fully validate ourapproach, and open the way for the application of the Bethe-Salpeter equationto large and complex systems.