Ab initio calculations of phonon properties and spectra in condensed matter

Abstract

Phonons, the quantization of atomic vibrations, are important in studying many solid state properties, ranging from Raman, infrared, and neutron scattering to thermal expansion, specific heat, and heat conductivity to electrical resistivity and superconductivity. Generally, modeling the interatomic forces and vibrational modes of a given system require costly computer simulations, though once calculated, they provide the means to a wide variety of phonon properties. Our goal is to enable easy access to these phonon properties and to do this, we have developed a framework for easily automating the workflows involved in interfacing a phonon mode calculation with the analysis tools for determining such physical properties. This was originally implemented with the AI2PS (ab initio to phonon spectra) tool, meant solely for the calculation of vibrational properties. It has since greatly expanded in scope and capabilities to a general scientific workflow tool called Corvus, which was started with the eventual goal of collecting all our various scientific workflow efforts—phonon properties, optical properties, and so on—into a single hub. We present here both the evolution of AI2PS into the Corvus project and the phonon properties simulated, including Debye–Waller factors, phonon contributions the electron self–energy and spectral function, vibrational free energy, thermal expansion, and heat capacity.