SIMPLE RELATIONSHIPS BETWEEN STATISTICAL-MECHANICS EXPECTATION VALUES

A general procedure for obtaining exact equations between statistical mechanics expectation values is suggested. The procedure is illustrate d for quantum and classical systems in a generalized ensemble. Detaile d applications are given for the Stockmayer potential in classical sta tistical thermodynamics. Application to site-site interactions is also discussed. The resulting equations can be used to detect inconsistenc ies in approximate theories. This is illustrated for the Percus-Yevick equations for hard chain molecules. For a complete description of equ ilibrium properties, additional information is needed to supplement th e derived equations. (C) 1996 American Institute of Physics.