Finite Temperature Effects on the X-ray Absorption Spectra of Crystalline Aluminas from First Principles

Angela F. Harper; Bartomeu Monserrat; Andrew J. Morris

paper

Finite Temperature Effects on the X-ray Absorption Spectra of Crystalline Aluminas from First Principles

arXiv:2206.10448

Abstract

By including phonon-assisted transitions within plane-wave DFT methods for calculating the X-ray absorption spectrum (XAS) we obtain the Al K-edge XAS at 300 K for two Al $_{2}$ O $_{3}$ phases. The 300 K XAS reproduces the pre-edge peak for $α$ -Al $_{2}$ O $_{3}$ , which is not visible at the static-lattice level of approximation. The 300 K XAS for $γ$ -Al $_{2}$ O $_{3}$ correctly describes two out of the three experimental peaks. We show that the second peak arises from 1s to mixed $s$ - $p$ transitions and is absent in the 0 K XAS. This letter serves as a basis for future applications, as the method is generalizable to any atom and edge.