The Ising model in the presence of a random field is investigated within the mean field approximation based on Landau expansion. The random field is drawn from the trimodal probability distribution P(hi)=pδ(hi−h0)+qδ(hi+h0)+rδ(hi), where the probabilities p,q,r take on values within the...

The Ising model, in the presence of a random field, is investigated within the mean-field approximation based on Landau expansion. The random field is drawn from the bimodal probability distribution P(h)=pδ(h−h0)+(1−p)δ(h+h0), where the probability p assumes any value within the interval...

The effects of bond randomness on the ground-state structure, phase diagram and critical behavior of the square lattice ferromagnetic Blume–Capel (BC) model are discussed. The calculation of ground states at strong disorder and large values of the crystal field is carried out by mapping the...

The influence of random site dilution on the critical properties of the two-dimensional Ising model on a square lattice was explored by Monte Carlo simulations with the Wang–Landau sampling. The lattice linear size was L=20–120 and the concentration of diluted sites q=0.1,0.2,0.3. Its pure...

Using Wang–Landau entropic sampling we study the Ising model in the framework of microcanonical ensemble (fixed magnetization). We are working for lattice size up to 1500×1500 in two dimensions and 100×100×100 in three dimensions. As we approach the coexistence curve from inside, varying...

The critical properties of the conserved-order-parameter (COP) version of the three-dimensional Ising model with zero magnetization were investigated by means of the Monte Carlo (MC) Wang–Landau algorithm. The study was carried out in appropriate restricted but dominant energy subspaces. The...

We study Baxter–Wu triangular model with fixed magnetization in the framework of canonical and microcanonical ensemble, constructing the density of states by Wang–Landau algorithm. We use an approximation similar to a recently developed scheme (critical minimum energy subspace). In this...

We use the recently developed critical minimum energy subspace (CrMES) approximation scheme to study the critical behavior of the Baxter–Wu model. This scheme uses only a properly determined part of the energy spectrum and allows us to obtain high accuracy for relatively large systems with...

The short-time critical dynamics of the Baxter–Wu model is investigated via Monte Carlo simulations using single spin-flip algorithms. The critical dynamic exponents z and θ are estimated and it is shown that the N-fold way provides a reliable estimate for the ratio of the static exponents...

Using a finite-size phenomenological theory we investigate the behavior of the Baxter–Wu model for both first- and second-order transitions. In order to distinguish between the two kinds of transition we study the finite-size scaling behavior of the order parameter and the susceptibility of...