Energy control of a molecular dynamics cell for the promotion of crystal phase transitions

A method for promoting crystal phase transitions in molecular dynamics (MD) simulations is proposed in which the temperature of a variable MD cell is controlled within the framework of the Parrinello-Rahman constant-pressure method. This control is independent of the temperature control of the molecules. The implementation makes it possible to perform MD simulations in which the temperature of the cell is high enough to enhance the deformation of the cell, while that of molecules is kept low so as not to lose the order of the crystal. The method successfully induced the phase transition of benzene crystals, which has not been obtained in MD simulations under usual conditions. Compared with the previously proposed method. i.e., momentum control of the cell, the present method is more favourable for reproducing experimentally observed structures.