A computer simulation of thermodynamic properties of solid Na

The recently derived pseudopotential of Rasolt and Taylor (1970, 1975) has been used to carry out a computer simulation of the properties of solid Na near its melting point. The authors have calculated the elastic constants, the thermodynamic Gruneisen parameter, the pressure, the specific heat and the quantity (dp/dT)v at both 293K and 361K. The calculation was performed for molar volumes that correspond roughly to those observed experimentally at zero pressure. A system composed of 250 particles is used, in which each atom is allowed to interact with its nearest 112 neighbours; periodic boundary conditions have been introduced to allow for the simulation of an infinite system. The overall agreement of the calculations with experimental data is good when one makes allowance for possible contributions from the electron gas terms. However, the shear constant c44, which contains no such contributing terms, is definitely smaller than the experimental values of Fritsch, Geipel and Prasetyo (1973). This may indicate an inadequacy of the pseudopotential.