CRITICAL-BEHAVIOR OF SOME 2D LATTICE MODELS

The density series of the non-interacting hard-square lattice gas mode l are reanalyzed by the ratio, Dlog Pade and differential approximant methods. The problem of poor consistency between series and other resu lts is resolved. Transfer matrix calculations are performed, implement ing both finite-size scaling and conformal invariance. Very accurate e stimates of the critical exponents y(t) and y(h) are obtained in agree ment with Ising universality. Furthermore, an improvement of the value of the critical density rho(c) is found. In addition, the universal c ritical-point ratios of the square of the second and the fourth moment of the magnetization for ferromagnetic Ising models on the square and on the triangular lattice with periodic boundary conditions are repor ted.