Atomistic modeling of amorphous silicon carbide: An approximate first-principles study in constrained solution space

TL;DR

This study introduces a first-principles atomistic modeling approach for amorphous silicon carbide, combining experimental data with ab initio simulations to produce realistic large-scale models that accurately reflect structural and electronic properties.

Contribution

It presents a novel constrained solution space method that integrates a priori structural information with ab initio optimization to efficiently model large amorphous SiC systems.

Findings

Produced realistic 1000-atom a-SiC models with excellent structural properties.

Identified predominant heteronuclear Si-C bonds and low defect concentrations.

Validated models against experimental and theoretical data.

Abstract

Localized basis ab initio molecular dynamics simulation within the density functional framework has been used to generate realistic configurations of amorphous silicon carbide (a-SiC). Our approach consists of constructing a set of smart initial configurations that conform essential geometrical and structural aspects of the materials obtained from experimental data, which is subsequently driven via first-principles force-field to obtain the best solution in a reduced solution space. A combination of a priori information (primarily structural and topological) along with the ab-initio optimization of the total energy makes it possible to model large system size (1000 atoms) without compromising the quantum mechanical accuracy of the force-field to describe the complex bonding chemistry of Si and C. The structural, electronic and the vibrational properties of the models have been studied and compared to existing theoretical models and available data from experiments. We demonstrate that the approach is capable of producing large, realistic configurations of a-SiC from first-principles simulation that display excellent structural and electronic properties of a-SiC. Our study reveals the presence of predominant short-range order in the material originating from heteronuclear Si-C bonds with coordination defect concentration as small as 5% and the chemical disorder parameter of about 8%.