Onsager reaction-field theory for magnetic models on diamond and hcp lattices

TL;DR

This paper extends the Onsager reaction-field theory to three-dimensional lattices with bases, applying it to predict critical temperatures of classical magnetic models on diamond and hcp lattices, and compares results with other methods.

Contribution

It generalizes the ORF theory to complex lattices and demonstrates its equivalence to Green's function approaches for hcp lattices.

Findings

Accurately predicts critical temperatures for magnetic models.

Shows ORF theory's equivalence to Green's function approach for hcp lattices.

Provides comparison with series extrapolations and other theories.

Abstract

The Onsager reaction-field (ORF) theory is extended so that it applies to any three-dimensional Bravais lattice with a basis. The ORF calculation is used to predict the critical temperature for classical Ising, XY, and Heisenberg magnetic models, in particular, on diamond and hexagonal close packed lattices. Results are compared with series extrapolations and other theoretical approaches where available. For the hcp lattice the ORF calculation is seen to be exactly equivalent to a Green's function approach.