Equation of state in 3-D Ising model from microscopic level calculation

A new method for derivating of the equation of state in the 3-D Ising model on the simple cubic lattice with the exponentially decreasing potential is proposed. This equation describes the order parameter of the system as a function of the temperature, external field and the microscopic parameters of the system in the critical region. Numerical investigation of this function is performed for the case when the potential parameters correspond to the nearest neighbours interaction.