Lambert W function of the critical temperature as a function of the anisotropic parameter in 2D square Ising model

Abstract

We consider the derived critical temperature (T_c) from the exact solution of the 2D square Ising model as a reference for approximation. Previous approximations accurately represent T_c as a function of the anisotropic parameter (α) only for low anisotropies. To accurately represent T_c at high anisotropies, we employed a limit approach with α approaching a large number. Additionally, we utilized the Lambert W function to express T_c as a function of α.