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

Abstract
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.

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