Validation of moment tensor potentials for fcc and bcc metals using EXAFS spectra

TL;DR

This study validates machine-learning moment tensor potentials for fcc and bcc metals by comparing MD simulation results with experimental EXAFS spectra, demonstrating their accuracy in reproducing atomic structures.

Contribution

First validation of moment tensor potentials against experimental EXAFS spectra for multiple metals, using active learning and DFT-based fitting.

Findings

Good agreement for W, Mo, and Cu with standard pseudopotentials.

Ni required a more accurate pseudopotential for similar accuracy.

EXAFS spectra effectively assess MTP performance in atomic structure reproduction.

Abstract

Machine-learning potentials for materials, namely the moment tensor potentials (MTPs), were validated using experimental EXAFS spectra for the first time. The MTPs for four metals (bcc W and Mo, fcc Cu and Ni) were obtained by the active learning algorithm of fitting to the results of the calculations using density functional theory (DFT). The MTP accuracy was assessed by comparing metal K-edge EXAFS spectra obtained experimentally and computed from the results of molecular dynamics (MD) simulations. The sensitivity of the method to various aspects of the MD and DFT models was demonstrated using Ni as an example. Good agreement was found for W, Mo and Cu using the recommended PAW pseudopotentials, whereas a more accurate pseudopotential with 18 valence electrons was required for Ni to achieve a similar agreement. The use of EXAFS spectra allows one to estimate the MTP ability in reproducing both average and dynamic atomic structures.