We have developed a new perturbation theory that extends our earlier perturbation theory of fluids to solids and that is reliable over a wide solid region. Characteristic features of this new theory are the use of an optimized reference potential whose repulsive range shrinks with density and its ability to deal with both harmonic and anharmonic thermodynamic properties on equal footing. Thermodynamic properties of facehyphen;centeredhyphen;cubic crystals are computed from the new theory for the Lennardhyphen;Jones system, the exponentialhyphen;6 system, and the inversenthhyphen;power (n=12, 9, 6, and 4) systems. Monte Carlo simulations are also performed to supplement available data. A comparison of theory and computer simulation shows excellent agreement, except for the softest repulsive system (n=4). The agreement extends from an anharmonic region near the melting line to a harmonic region, where the hardhyphen;sphere reference system achieves close to 92percnt; of the closehyphen;packed density. Beyond this region errors in the analytic fits to the hardhyphen;sphere radial distribution functions used in this work make an accurate test of the new theory difficult. Since the present formulation is the same for both solid and fluid phases, we used the theory to compute the melting and freezing data of the aforementioned model systems. Agreement with the corresponding Monte Carlo data is satisfactory. Comparison with other theoretical models of solids is also discussed.
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