The model of the ideal crystal as a criterion for evaluating of the   approximate equations of the liquids
  It is necessary for the statistical description of collective effects in liquids to set that or other approximation between direct and pair correlation functions which describe a neighboring order. The analytical solution of the generalized Ornstein-Zernike (OZ) equation was obtained for a system of particles at T=0. It is shown that in this limit case the neighboring order disappears and the direct correlation function describes a distant order which is typical for the ideal crystal. The approximation correctly describing the limit transition liquid-solid at T=0 will have a physical meaning. 
Yu.V. Agrafonov and A.G. Balakhchi (Irkutsk State University)