Construction of Amorphous Structure Models via Relaxation of Random Arrangements of Molecules

Amorphous materials have long been used in various technological applications, including semiconductor-based electronics. However, modeling amorphous materials at an atomic scale remains challenging. The melt-quench method is commonly used to generate models of amorphous structures, but the necessary lengthy molecular dynamics runs can make calculations prohibitively expensive, especially for ab initio molecular dynamics. Furthermore, the relevance of melt-quench to athermal techniques like low-temperature deposition is unclear. We present an alternative method for constructing amorphous structures that starts with randomly placing molecules in a large box, followed by relaxation of the cell and atomic positions. We apply this approach to a variety of amorphous systems, using ab initio density functional theory for the energetics, and obtain good agreement with experimental densities and radial distribution functions with less computational cost than the melt-quench method.