MONTE-CARLO RENORMALIZATION-GROUP STUDY OF THE SITE-DILUTED SIMPLE-CUBIC ISING-MODEL

The Monte Carlo renormalization-group approach is applied to investigate the critical behavior of the simple-cubic Ising model diluted randomly with nonmagnetic atoms of concentration x. For x=0.2 a value of x=0.688(13) is found which is well above the result =0.629(4) for the pure model and above the exact lower bound of =2/3, and the relative width of the asymptotic regime is definitely larger than 3×10-4. For x=0.1 the obtained value is below the exact lower bound, possibly indicating that the asymptotic critical regime has not been penetrated, that this regime has a width smaller than 1.3×10-4, and that it can hardly be explored by experiments or computer simulations. © 1990 The American Physical Society.