改进压缩性近似并导出新的硬球微扰理论表达式

提出在Barker与Henderson的压缩性近似推导中,相邻壳层之间的分子数应该相关,导出了相关系数和改进的二级微扰项,提高了高级微扰项在较高密度区的准确性。对二级以上的高级微扰项采用Barker与Henderson的近似方法,得到一个简单的微扰理论表达式,以硬球势为参考势,方阱势为微扰势,用一新的级数形式的径向分布函数导出了自由能、内能、比热、压缩因子的级数表达式。其四项截断式的计算结果与MC、MD计算机模拟值符合较好。

Improvement of Compressibility Approximation and Derivation of New Hard Sphere Perturbation Theory Representation

Barker and Henderson's Compressibility approximation is improved by assuming that the numbers of molecules in neighbour spherical shells are correlated.The results are better than those of Barker and Henderson's Macroscopic Compressibility Approximation (B-H Ma.Appro.) and Local Compressibility Approximation(B-H Lo.C. Appro .) specially at high densities.A simple and accurate analytic representation of square-well potential hard sphere perturbation theory is derived based upon this improvement.A new form of radial distribution function is proposed and applied.The theory is tested by calculating thermodynamic properties with the four-term truncated form, and the results are in good agreement with those of Monte Carlo and Molecular Dynamics computer simulation calculations.