The structure and migration of twin boundaries in tetragonal $\beta$-Sn: an application of machine learning based interatomic potentials

TL;DR

This study combines machine learning-based interatomic potentials with experimental TEM data to analyze twin boundary structures and migration mechanisms in tetragonal $eta$-Sn, revealing new low-energy interface types.

Contribution

It introduces ML-based interatomic potentials specifically developed for $eta$-Sn, enabling detailed atomistic simulations of twinning in this low-symmetry material.

Findings

ML potentials agree with TEM observations

Identification of faceted twin boundaries

Discovery of low-energy asymmetric PA/AP interfaces

Abstract

Although atomistic simulations have contributed significantly to our understanding of twin boundary structure and migration in metals and alloys with hexagonal close packed (HCP) crystal structures, few direct atomistic studies of twinning have been conducted for other types of low symmetry materials, in large part due to a lack of reliable interatomic potentials. In this work, we examine twin boundary structure and migration in a tetragonal material, $\beta$-Sn, comparing high resolution Transmission Electron Microscopy (TEM) images of deformation twins in $\beta$-Sn to the results of direct atomistic simulations using multiple interatomic potentials. ML-based potentials developed in this work are found to give results consistent with our experimental data, revealing faceted twin boundary structures formed by the nucleation and motion of twinning disconnections. We use bicrystallographic methods in combination with atomistic simulations to analyze the structure, energy and shear coupled migration of observed twin facets in $\beta$-Sn. In analogy to Prismatic-Basal (PB/BP) interfaces in HCP metals, we discover low energy asymmetric Prismatic-A-plane (PA/AP) interfaces important to twin growth in $\beta$-Sn. A Moment Tensor Potential (MTP) and Rapid Artificial Neural Network (RANN) interatomic potential suitable for studying twinning and phase transformations in Sn are made publicly available as part of this work.