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.