SELF-CONSISTENT ORNSTEIN-ZERNIKE APPROXIMATION FOR LATTICE GASES

A self-consistent approximation for the structure factor of three-dime nsional lattice gases yields remarkably accurate predictions (less tha n 3% error over most of the temperature range) for the correlation len gth, isothermal compressibility, specific heat, and the coexistence cu rve. Critical temperatures agree to within 0.2%, and other critical pr operties to within (1-2)%, of the best numerical estimates. Until temp erature and density are within 1% of their critical values, the approx imate effective critical exponents do not differ appreciably from thei r estimated exact form; they attain their limiting spherical-model val ues only much closer to critical. The method should prove useful for a variety of three-dimensional lattice-gas and fluid problems; it is in appropriate to two dimensions, where it predicts criticality at zero t emperature.