用集团展开法计算二元体系的物态方程

二元混和系统的总势能可看作是系统所含粒子坐标的函数，采用集团展开法处理二元液体，直接计算其配分函数或物态方程比较因难。得到了二元液体配分函数的二阶近似和三阶近似，并计算了硬球体系的物态方程。结果表明，对于低密度二元液体，其二阶近似计算的偏差不超过５％，其三阶项可当作微扰进行处理；对于密度较高的液体，则应采用三阶近似甚至四阶近似。

CALCULATION OF STATE EQUATION IN BINARY SOLUTION BY USING CLUSTER INTEGRAL METHOD

The binary solution can be considered as a canonical ensemble, in which the state equation can not be calculated directly by using many dimension integral methods.In the theory about liquid, it is very important to use correlation function or radial distribution function.The calculation of these functions,however,must employ some approximation methods, such as HNC and P Y approximation, that may cause considerable errors while describing real liquid. In this paper, the second term and third term of the configurational partition function are calculated by using a cluster integral method.It is found that the result from this method is in agreement with experimental data and P Y approximation when the density of the liquid is small.