X-ray absorption Debye-Waller factors from ab initio molecular dynamics

TL;DR

This paper introduces an ab initio molecular dynamics method to compute temperature-dependent Debye-Waller factors in x-ray spectra, avoiding explicit phonon calculations and providing vibrational and thermal properties.

Contribution

The paper presents a novel ab initio approach to calculate Debye-Waller factors directly from molecular dynamics simulations without explicit phonon mode analysis.

Findings

Accurately computes Debye-Waller factors across various systems.

Provides vibrational density of states and thermal quantities.

Shows good agreement with experimental data.

Abstract

An ab initio equation of motion method is introduced to calculate the temperature-dependent mean square vibrational amplitudes which appear in the Debye-Waller factors in x-ray absorption, x-ray scattering, and related spectra. The approach avoids explicit calculations of phonon-modes, and is based instead on calculations of the displacement-displacement time correlation function from ab initio density functional theory molecular dynamics simulations. The method also yields the vibrational density of states and thermal quantities such as the lattice free energy. Illustrations of the method are presented for a number of systems and compared with other methods and experiment.