Molecular dynamics simulations of temperature- and pressure-induced solid–solid phase transitions in crystalline para-terphenyl

Abstract

Molecular dynamics (MD) simulations of pressure- and temperature-induced solid–solid phase transitions in para-terphenyl have been investigated using Material Studio®. Initial simulations were performed using the COMPASS (condensed-phase optimised molecular potentials for atomistic simulation studies) force field to evaluate its ability to model the known temperature and pressure phase boundary between the triclinic and monoclinic crystal phases. Geometry optimisation using the universal COMPASS force field could not adequately model the experimental crystal structure at 113 K, and MD simulations could not adequately reproduce the known transition temperature at ambient pressure, nor yield a well-defined transition pressure at low temperature. However, a one-parameter optimisation of the torsion potential component of the polymer-consistent force field (PCFF) (incorporating COMPASS non-bond parameters) yielded MD simulations that accurately modelled the pressure–temperature boundary between the low-temperature low-pressure triclinic phase and the high-pressure high-temperature monoclinic phase of para-terphenyl.