ISOTHERMAL COMPRESSIBILITY AND CORRELATION RADIUS NEAR THE CRITICAL-POINT - NUMERICAL-ANALYSIS OF THE ORNSTEIN-ZERNIKE EQUATION

Solution of the Ornstein-Zernike equation is analyzed numerically in t he Percus-Yevick and hyperchain approximations for a system of Lennard -Jones particles in a critical region. The temperature dependences of correlation functions, isothermal compressibility chi, and correlation radius of density fluctuations xi are investigated at a critical dens ity; the corresponding critical indices are determined It is shown tha t the Percus-Yevick approximation yields satisfactory results when the correlation functions are calculated within a range corresponding to approximately 50 atomic (molecular) diameters. In this case, with appr oximate to 5% deviations from the critical temperatute, the calculated and experimental values of chi and critical indices are in good agree ment.