Surface energy and stability of stress-driven discommensurate surface structures

TL;DR

This paper introduces an ab initio method to estimate upper and lower bounds of surface energies for stress-driven discommensurate structures, including non-periodic and large unit cell surfaces, with applications to Si(111):Ga and Ge(111):Ga.

Contribution

It provides a novel approach to bound surface energies of complex discommensurate structures using ab initio calculations, addressing non-periodic and large-unit-cell challenges.

Findings

Surface energies of Si(111):Ga and Ge(111):Ga phases determined within ±0.2 eV.

Upper bounds derived from instability of stressed, commensurate parent structures.

Lower bounds obtained from hypothetical, strained, but ideally commensurate surfaces.

Abstract

A method is presented to obtain {\it ab initio} upper and lower bounds to surface energies of stress-driven discommensurate surface structures, possibly non-periodic or exhibiting very large unit cells. The instability of the stressed, commensurate parent of the discommensurate structure sets an upper bound to its surface energy; a lower bound is defined by the surface energy of an ideally commensurate but laterally strained hypothetical surface system. The surface energies of the phases of the Si(111):Ga and Ge(111):Ga systems and the energies of the discommensurations are determined within $\pm 0.2$ eV.