Comparing empirical interatomic potentials to modeling silicon surface stress

Abstract

This study compares six widely used classical many-body potentials – Tersoff-T3, Stillinger–Weber, modified Tersoff, optimized modified Tersoff, environment-dependent interatomic potential and modified embedded atom method – to model silicon surface stress. Functional forms for all potentials are first analyzed to determine atomic stress. This is then followed by a set of surface stress analysis on silicon {100} and {110} surfaces. A significant difference between those potentials is observed to calculate the surface stress in silicon crystal. The Tersoff-T3 and environment-dependent interatomic potentials demonstrate a significant surface stress in unreconstructed silicon {100} and {110} surfaces, while the Stillinger–Weber potential estimates a negligible surface stress. The implication of the surface stress is studied on the mechanical response of silicon nanowires. A dramatic contrast between potentials is recognized to calculate the equilibrium elongation due to the surface stress in silicon nanowires along <100> crystal orientation. While the environment-dependent interatomic potential predicts a contraction in the equilibrium elongation in relaxed nanowires, the Tersoff-T3 potential exhibits a considerable uniaxial expansion in silicon nanowires comparable with density functional theories. Findings in this work give more insight into the capability of empirical interatomic potentials to capture the surface stress in silicon nanostructures.