Finite-temperature self-energy correction to XANES

Calculation of the complex-valued self-energy is a bottleneck in the calculation of excited state properties such as x-ray absorption spectra (XAS). To circumvent this problem, Lu et al. [1] introduced a low order polynomial function to approximate the Hedin-Lundqvist (HL) self-energy [2, 3] at zero temperature. In this work, we take the same approach to obtain an approximation to the RPA GW quasiparticle self-energy at finite temperature [4]. Finally, we present calculations of XAS for several materials.

[1] D. Lu, J. de Leon, and J. Rehr, Physica B: Condensed Matter 158, 413 (1989).

[2] B. I. Lundqvist, Physik der kondensierten Materie 6, 206 (1967).

[3] L. Hedin and S. Lundqvist (Academic Press, 1970) pp. 1–181.

[4] T. S. Tan, J. J. Kas, and J. J. Rehr, Phys. Rev. B 98, 115125 (2018).