Structure of solid t-butyl cyanide: a study by means of constant-temperature, constant-pressure, molecular dynamics simulation

The structural phase transition that occurs in solid t‐butyl cyanide just before melting has been studied by constant‐temperature, constant‐pressure, molecular‐dynamics simulations. The simulations were based on a six‐site potential model with parameters obtained from static‐energy calculations for the observed, low‐temperature, monoclinic structure. Changes in the lattice constants and in order parameters for the molecular orientations show that an apparently first‐order transition to a tetragonal, orientationally disordered phase occurs at a temperature in the range between 250 and 275 K; experimentally, a similar transition is observed at 233 K. Comparison is made with neutron‐scattering results for the tetragonal phase, and deficiencies in the potential model and in the model used to parametrize it are discussed.