Advanced approach to the local structure reconstruction and theory validation on the example of the W L$_3$-edge extended X-ray absorption fine structure of tungsten

TL;DR

This study combines atomistic simulations and advanced analysis methods to explore the local structure and validate interaction models of tungsten using W L3-edge EXAFS data, revealing insights into atomic motion and thermal disorder.

Contribution

It introduces a combined MD-EXAFS and RMC-EXAFS approach to analyze tungsten's local structure and validate interaction potentials beyond the first coordination shell.

Findings

Atomic motion correlation in tungsten negligible above 8 Å.

EXAFS data can determine mean-square displacements of individual tungsten atoms.

Validation of embedded atom and modified embedded atom potentials.

Abstract

Atomistic simulations of the experimental W L$_3$-edge extended X-ray absorption fine structure (EXAFS) of bcc tungsten at T = 300 K were performed using classical molecular dynamics (MD) and reverse Monte Carlo (RMC) methods. The MD-EXAFS method based on the results of MD simulations allowed us to access the structural information, encoded in EXAFS, beyond the first coordination shell and to validate the accuracy of two interaction potential models - the embedded atom model potential and the second nearest-neighbor modified embedded atom method potential. The RMC-EXAFS method was used for more elaborate analysis of the EXAFS data giving access to thermal disorder effects. The results of both methods suggest that the correlation in atomic motion in bcc tungsten becomes negligible above 8 {\AA}. This fact allowed us to use the EXAFS data to determine not only mean-square relative displacements of atomic W-W pair motion but also mean-square displacements of individual tungsten atoms, which are usually accessible from diffraction data only.