Atomistic simulations of nanoindentation in single crystalline tungsten: The role of interatomic potentials

TL;DR

This study uses molecular dynamics simulations with various interatomic potentials to analyze nanoindentation in tungsten, revealing differences in dislocation mechanisms and demonstrating the accuracy of a machine-learned potential compared to traditional models.

Contribution

It introduces a machine-learned Gaussian approximation potential for tungsten and compares its performance with traditional potentials in nanoindentation simulations.

Findings

Similar load-displacement curves across models

Discrepancies in dislocation nucleation mechanisms

TabGAP shows highest accuracy compared to DFT and experiments

Abstract

Computational modeling is usually applied to aid experimental exploration of advanced materials to better understand the fundamental plasticity mechanisms during mechanical testing. In this work, we perform Molecular dynamics (MD) simulations to emulate experimental room temperature spherical-nanoindentation of crystalline W matrices by different interatomic potentials: EAM, modified EAM, and a recently developed machine learned based tabulated Gaussian approximation potential (tabGAP) for describing the interaction of W-W. Results show similarities between load displacements and stress-strain curves, regardless of the numerical model. However, a discrepancy is observed at early stages of the elastic to plastic deformation transition showing different mechanisms for dislocation nucleation and evolution, that is attributed to the difference of Burgers vector magnitudes, stacking fault and dislocation glide energies. Besides, contact pressure is investigated by considering large indenters sizes that provides a detailed analysis of screw and edge dislocations during loading process. Furthermore, the glide barrier of this kind of dislocations are reported for all the interatomic potentials showing that tabGAP model presents the most accurate results with respect to density functional theory calculations and a good qualitative agreement with reported experimental data