Nanoindentation of tungsten: From interatomic potentials to dislocation plasticity mechanisms

Abstract

In this study, we employed molecular dynamics simulations, both traditional and machine learned, to emulate spherical nanoindentation experiments of crystalline W matrices at different temperatures and loading rates using different approaches, such as EAM, EAM with Ziegler, Biersack, and Littmark corrections, modified EAM, analytic bond-order approach, and a recently developed machine-learned tabulated Gaussian approximation potential (tabGAP) framework for describing the W-W interaction and plastic deformation mechanisms. Results showed similarities between the recorded load-displacement curves and dislocation densities, for different interatomic potentials and crystal orientations at low and room temperature. However, we observe concrete differences in the early stages of elastic-to-plastic deformation transition, revealing different mechanisms for dislocation nucleation and dynamics during loading, especially at higher temperatures. This is attributed to the particular features of orientation dependence in crystal plasticity mechanisms and, characteristically, the stacking fault and dislocation glide energies information in the interatomic potentials, with tabGAP being the one with the most well-trained results compared to density functional theory calculations and experimental data.