A study of the condensed phases and solid–solid phase transition in toluene: A Monte Carlo investigation

A Monte Carlo study of the orthorhombic(beta), monoclinic(alpha), and liquid phases of toluene in the isobaric isothermal ensemble employing variable shape simulation cell is reported here. The intermolecular potential of Williams and Starr is seen to reproduce the lattice parameters and other known properties reasonably well for the alpha-phase. The beta-phase is not reproduced as well. The structure has been characterized in terms of the radial distribution functions and orientational correlation functions. The transition from the orthorhombic low temperature beta-phase to the high temperature monoclinic alpha-phase has been successfully simulated. The transition is first order and lies between 140 and 145 K in agreement with experiment. The reverse transition from the alpha- to the beta-phase does not take place in agreement with experiment. The liquid phase density and the heat of vaporization are reproduced well. The potential employed predicts an interaction energy which is about 5% in excess of the experimental value. The orientational correlation function and the radial distribution functions are sensitive to the potential and suggest where improvements are possible.