Randomly dilute two dimensional Ising models

Calculations of the specific heat and magnetization of quenched, site‐diluted, N×N square and triangular Ising lattices have been carried out by a Monte Carlo method. For spin concentrations x of 0.8 and 0.9, lattices of size N=64 did not give sharp transitions. For a triangular lattice with N=128 and x=0.904, we found a well‐defined peak in the specific heat and an abrupt change in the magnetization at T=0.865 Tc(1). Linear interpolation gives s≡d/dx[Tc(x)/Tc(1)]x=1=1.40±0.05, in excellent agreement with the high temperature series calculations of Rushbrooke et al. For the square lattice we calculate s=1.5±0.1. We also determined site magnetization as a function of the number of ’’live’’ nearest neighbors.