A MOLECULAR-DYNAMICS SIMULATION OF HCL - A STUDY OF THE VIBRATIONAL DEPHASING MECHANISM

Molecular dynamics simulations are performed for a hydrogen chloride system using a new effective pair potential at three different temperatures and physical states: at 110 K (corresponding to a solid, disordered cubic phase), at 195 K (liquid phase, slightly above the melting point) and at 300 K (liquid phase). The structure of HCl in going from the crystal lattice to liquid at room temperature is well described. Translational motion in the liquid is slightly too slow while the angular and the reorientational motions are reasonably well described. The temperature variations are in reasonable agreement with experiment. The vibrational correlation functions decay too slowly so consequently the line shapes are too narrow. The red gas-to-liquid shift is also found to be too small. All the normal coordinate derivatives are directly calculated from the potential function. It is, therefore, assumed that very accurate interaction potentials are needed in order to calculate the vibrational dephasing mechanisms from the MD simulations within the present theory.