Predicting interface structures: From SrTiO$_3$ to graphene

TL;DR

This paper introduces a first-principles method using ab initio random structure searching (AIRSS) combined with DFT to predict atomic interface structures, successfully identifying new low-energy configurations in graphene and SrTiO3 interfaces.

Contribution

The paper presents a transferable, efficient, and simple first-principles approach for predicting interface structures applicable to various materials.

Findings

Discovered new low-energy grain boundary structures in graphene.

Identified previously unknown low-energy structures in SrTiO3 with different stoichiometries.

Predicted long-range distortions emanating from the interface into the bulk.

Abstract

We present here a fully first-principles method for predicting the atomic structure of interfaces. Our method is based on the {\it ab initio} random structure searching (AIRSS) approach, applied here to treat two dimensional defects. The method relies on repeatedly generating random structures in the vicinity of the interface and relaxing them within the framework of density functional theory (DFT). The method is simple, requiring only a small set of parameters that can be easily connected to the chemistry of the system of interest, and efficient, ideally adapted to high-throughput first-principles calculations on modern parallel architectures. Being first-principles, our method is transferable, an important requirement for a generic computational method for the determination of the structure of interfaces. Results for two structurally and chemically very different interfaces are presented here, grain boundaries in graphene and grain boundaries in strontium titanate (SrTiO$_3$). We successfully find a previously unknown low energy grain boundary structure for the graphene system, as well as recover the previously known higher energy structures. For the SrTiO$_3$ system we study both stoichiometric and non-stoichiometric compositions near the grain boundary and find previously unknown low energy structures for all stoichiometries. We predict that these low energy structures have long-range distortions to the ground state crystal structure emanating into the bulk from the interface.