Truncation procedure for high order reduced distribution functions

The problem of the compatibility of the results obtained from approximate expressions for the junior distribution functions is viewed under a broad aspect. This paper concerns the compatibility of the calculated values of not only the energy and pressure but also of the higher-order derivatives of the free energy with respect to the thermodynamic variables (such as the heat capacity) as well as of the chain of integro-differential equations, the normalization relations, and the satisfaction of the correlation weakening conditions. The degree of agreement with the requirements mentioned is suggested to be useful as a possible a priori measure of applicability of a certain approximation adopted for calculating the correlation functions over a wide range of thermodynamic variables. The consideration is made within the framework of the conditional distribution method.