Ab initio study of the structure and properties of amorphous silicon hydride from accelerated molecular dynamics simulations

TL;DR

This study uses accelerated ab initio molecular dynamics to generate extensive models of amorphous silicon hydride, revealing defect-free structures with pristine band gaps and detailed hydrogen microstructures, validated against experimental data.

Contribution

It introduces a large-scale, high-quality modeling approach combining metadynamics and first-principles calculations for amorphous silicon hydride.

Findings

Models are defect-free with pristine band gaps.

Hydrogen distribution varies from isolated to clustered environments.

Results agree with multiple experimental techniques.

Abstract

This paper presents a large-scale $ab$ $initio$ simulation study of amorphous silicon hydride ($a$-Si$_{\text{1-x}}$H$_{\text{x}}$) with an emphasis on the structure and properties of the material across a range of hydrogen concentration by combining accelerated molecular dynamics (MD) simulations with first-principles density-functional calculations. The accelerated MD scheme relied on classical metadynamics, which enabled the development of 2600+ high-quality structural models of $a$-Si$_{\text{1-x}}$H$_{\text{x}}$, with system sizes ranging from 150 to 6,000 atoms and hydrogen concentrations vary from 6 to 20 at. %H. The resulting amorphous networks were found to be completely free from any coordination defects and that they all exhibited a pristine band-gap in their electronic spectrum. The microstructural properties of hydrogen distributions were examined with great emphasis on the presence of isolated and clustered environments of hydrogen atoms. The results were compared with a suite of experimental data obtained from x-ray diffraction, infrared spectroscopy, spectroscopic ellipsometry and nuclear magnetic resonance studies.