Improvements on the Natural Iteration Method in the cluster variation method

By examining the relationship between grand potential and various distribution variables, this paper combines the Natural Iteration Method (NIM) with the Step Speeded Method and Dichotomous method, respectively, and proposes two methods, Step Speeded- and Dichotomous-NIMs, for improving the conventional NIM by making use of the absolute convergence of the NIM. The calculated results indicate the numbers of iteration in the two methods obviously decreased, and they are still with absolute convergence.