X-ray Absorption Near-Edge Structure calculations with pseudopotentials. Application to K-edge in diamond and alpha-quartz

TL;DR

This paper introduces a reciprocal-space pseudopotential method for calculating XANES spectra, effectively handling core-hole interactions in large supercells and comparing results with the Bethe-Salpeter approach.

Contribution

A novel reciprocal-space pseudopotential scheme for XANES calculations that efficiently incorporates core-hole effects using large supercells.

Findings

Method accurately reproduces experimental XANES spectra.

Core-hole effects depend on supercell size, influencing spectral features.

Comparison shows advantages over Bethe-Salpeter approach in certain cases.

Abstract

We present a reciprocal-space pseudopotential scheme for calculating X-ray absorption near-edge structure (XANES) spectra. The scheme incorporates a recursive method to compute absorption cross section as a continued fraction. The continued fraction formulation of absorption is advantageous in that it permits the treatment of core-hole interaction through large supercells (hundreds of atoms). The method is compared with recently developed Bethe-Salpeter approach. The method is applied to the carbon K-edge in diamond and to the silicon and oxygen K-edges in alpha-quartz for which polarized XANES spectra were measured. Core-hole effects are investigated by varying the size of the supercell, thus leading to information similar to that obtained from cluster size analysis usually performed within multiple scattering calculations.