ORNSTEIN-ZERNIKE DERIVATIVE RELATIONS AND THERMODYNAMIC FUNCTIONS

The consequences of the derivatives of the Ornstein-Zernike relation with respect to the density (rho) and temperature (T) are examined. An approximate closure for the Ornstein-Zernike relation is used to evaluate the derivatives of the pair-correlation function to all orders without knowing explicitly the correlation functions higher in order than the pair-correlation function. The first- and second-order thermodynamic (rho or T) derivatives of the pair-correlation function are calculated and compared with the experiments of Egelstaff et al. In addition, the thermodynamic functions involving these derivatives are evaluated to demonstrate the utility and accuracy of the method.