Generalized approach to description of energy distribution of spin system

We examined energy spectrums of some particular systems of N binary spins. It is shown that the configuration space can be divided into N classes, and in the limit N → ∞ the energy distributions in these classes can be approximated by the normal distributions. For each class we obtained the expressions for the first three moments of the energy distribution, including the case of presence of a nonzero inhomogeneous magnetic field. We also derived the expression for the variance of the quasienergy distribution in the local minimum. We present the results of computer simulations for the standard Ising model and the Sherrington–Kirkpatrick and Edwards–Anderson models of spin glass. Basing on these results, we justified the new method of the partition function calculation.