Pressure effect on the atomic structure of amorphous silicon

Abstract

Context

This study explores how hydrostatic pressure influences the atomic structure of amorphous silicon. As pressure increases, the material undergoes densification, reflected in the shift of radial distribution functions and bond angle distributions. While the short-range order undergoes relatively small structural variations, the medium-range order exhibits significant structural rearrangements, including changes in coordination numbers and atomic connectivity. These pressure-induced transformations favor simpler, more compact atomic configurations. The resulting structural reorganization leads to increased internal energy and reduced atomic volume, revealing the energetic cost of compression. Overall, the findings offer insights into the fundamental behavior of amorphous silicon under extreme conditions.

Methods

Molecular dynamics simulations were conducted using the Tersoff potential for LAMMPS to study amorphous silicon. The samples were prepared using a cooling rate of 10\(^{11}\) K/s and then relaxed at 100 K at six different pressures: 0, 2, 4, 6, 8, 10 GPa. Structural properties were calculated using radial distribution functions, bond angle distribution, Voronoi analysis, and atomic volumes, and network analysis was conducted to quantify connectivity among four-coordinated atoms. Calculations were performed using the OVITO software and Python programming language.