Mean-field description of structural phase transitions in a hypercubic lattice model

We examine the mean-field theory investigation of a hypercubic lattice model that exhibits structural phase transitions. In this model, with anharmonicity as main characteristic and displacement-displacement stiffness constant, the occurrence of phase transitions mechanism is analyzed and the effects of the anharmonicity on the order of the transition are studied. Discussing the features of the Hamiltonian, thermodynamic properties calculated show the occurrence of the structural phase transitions, which are either (i) a second-order transition (characteristic of short-range attractive part of the double-Morse one-site potential) or (ii) a first-order transition with sharp melting transition and bifurcation entropy, depending on the strength of the anharmonicity.