Phase transitions in a sequence of crystal(C)-smecticA(SmA)-nematic(N)-isotropic(I) phases are investigated by constant pressure molecular-dynamics (MD) simulations, in which the hydrostatic pressure is preserved. The present MD simulation uses a simple model that represents soft spherocylinders with both translational and orientational freedoms. This model enables us to investigate to what extent the properties known to real liquid crystal phases can be explained by the anisotropy of the molecular shape alone. The phase transitions are manifested not only in the macroscopic properties, such as enthalpy, but also in the microscopic properties as well. Anisotropic diffusion of molecules in liquid crystal phases is also investigated.