MAGNETIC-SUSCEPTIBILITY AND SPECIFIC-HEAT OF THE 2-DIMENSIONAL ISING-MODEL WITH THE NEAREST, OR UP TO THE NEXT NEAREST-NEIGHBOR INTERACTIONS

In the Ising model on a helical lattice with period M (in the limit M-->infinity of this lattice, the model corresponds to the two-dimensional Ising model), the exact simultaneous equations to calculate physical quantities are derived. The zero field magnetic susceptibility chi0, and also the specific heat C are obtained numerically for the system of M less-than-or-equal-to 11. Furthermore, in the Ising model with up to the next nearest neighbor interactions on the helical lattice, chi0 and C are calculated for the system of M less-than-or-equal-to 9. The results obtained are an excellent approximation to the exact chi0 and C of the two-dimensional systems.