Abstract
First-principles theory was developed to study the structural phase transformations in the Laves phase HfV2 alloy. We explored the
energy landscape and established the role of lattice anharmonicity underlying the structural phase transitions. Our approach is based on
a phenomenological Landau theory for the structural phase transition and a mean-field approximation for the free energy. First-principles
calculations were utilized to obtain the distortion energy as a function of relevant deformations, and to deduce parameters for
constructing the free energy. Our result for the phase transition temperature of HfV2 is in good agreement with experiment. We find that
the high-temperature cubic C15 phase is stabilized by the effect of lattice anharmonicity. The theory also predicts an anomalous increase
in shear modulus with increasing temperature for systems where the anharmonicity is pronounced.