ISING UNIVERSALITY IN 3 DIMENSIONS - A MONTE-CARLO STUDY

We investigate three Ising models on the simple cubic lattice by means of Monte Carlo methods and finite-size scaling. These models are the spin-1/2 Ising model with nearest-neighbour interactions, a spin-1/2 m odel with nearest-neighbour and third-neighbour interactions, and a sp in-1 model with nearest-neighbour interactions. The results are in acc urate agreement with the hypothesis of universality. Analysis of the f inite-size scaling behaviour reveals corrections beyond those caused b y the leading irrelevant scaling field. We find that the correction-to -scaling amplitudes are strongly dependent on the introduction of furt her-neighbour interactions or a third spin state. In a spin-1 Ising mo del, these corrections appear to be very small. This is very helpful f or the determination of the universal constants of the Ising model. Th e renormalization exponents of the Ising model are determine as y(t) = 1.587 (2), y(h) = 2.4815 (15) and y(i) = -0.82 (6). The universal rat io Q = (m(2))(2)/(m(4)) is equal to 0.6233 (4) for periodic systems wi th cubic symmetry. The critical point of the nearest-neighbour spin-1/ 2 model is K-c = 0.2216546 (10).