Abstract
A method is presented to calculate high-temperature series expansions. It is worked out on the -dimensional Ising model with interactions of arbitrary but finite range. Improved mean-field approximations are proposed and applied to a model for the ammonium halides. The phase diagram is calculated. It exhibits a tricritical point in agreement with the experimental observation.
- Received 23 November 1981
DOI:https://doi.org/10.1103/PhysRevB.25.5875
©1982 American Physical Society