Ising diatomic molecules in the mean-field and exact recursion relations approach

Abstract

This research utilizes a mean field theory (MFT) on spin-1/2 diatomic molecules for the first time to obtain the thermal changes in magnetizations for each molecule, thus generating the phase diagrams. The same model was also studied using the Bethe lattice (BL) approach in terms of the exact recursion relations (ERR) in order to compare its results with the MFT results. Different types of bilinear interaction parameters between the constituents of a molecule and nearest-neighbor (NN) molecules were assumed, and the coordination number is set to three, corresponding to the honeycomb lattice. It is found that the MFT only gives second-order phase transitions, but the ERR approach gives various phase transitions. The obtained results show that the ERR approach on the BL is superior over the MFT since it provides many more details of the model.