All-electron Implementation of Bethe-Salpeter Equation Method: Development and Application

A new all-electron implementation of the Bethe-Salpeter Equation (BSE) method for optical excitations is presented. We benchmarked the accuracy of our implementation¹ on low lying optical excitations of organic molecules in the Thiel benchmark set² for validation, and the basis-set dependence is carefully analyzed. We then integrated the core-GW approach by Golze et al.³ into our BSE implementation for X-ray absorption spectroscopy (XAS). We compare our results for K-edge XAS spectra of small organic molecules to earlier EOM-CCSD work by Peng et al⁴. We found the accuracy of our BSE approach is comparable to or better than EOM-CCSD, which gives the errors within 0.5 eV of experimental value for the test set. The implementation for extended periodic systems is discussed lastly with examples of liquid water and crystalline silicon.

¹ Chi Liu, et al., arXiv preprint arXiv:1908.01431 (2019).
² Marko Schreiber et al., The Journal of Chemical Physics 128 (13), 134110 (2008).
³ Dorothea Golze et al., Journal of Chemical Theory and Computation 14 (9), 4856 (2018).
⁴ Bo Peng et al., Journal of Chemical Theory and Computation 11 (9), 4146 (2015).