Phase Transition in 2D Ising Model with Next-Neighbor Interaction

We used a Monte Carlo method to analyze a planar Ising model taking into account a ferromagnetic interaction with next neighbors. We found that independent of the value of the additional interaction, the character of singularity of the heat capacity did not change. Namely, at the critical point the heat capacity has a logarithmic singularity. We obtained a semi-theoretical formula relating the value of the critical temperature with the value of the additional ferromagnetic interaction. (paper)