The results of density functional calculations of the structural and vibrational properties of molecules related to polycarbonate have been used to optimize the parameters describing a classical atomistic force field. This field has then been used in extensive Monte Carlo and molecular dynamics simulations of crystalline, amorphous, and liquid polycarbonate systems. Applications include thermal properties of crystal and liquid phases, the glass transition, and vibrational properties and surface structure of the amorphous material. Molecular dynamics calculations using both this force field (DF-ff) and one derived from MD simulations of liquids (liq-ff) describe reasonably well the structure factor of amorphous bisphenol A polycarbonate.