Ab initio quasiharmonic equations of state for dynamically stabilized soft-mode materials

Drummond, Neil and Ackland, G. J. (2002) Ab initio quasiharmonic equations of state for dynamically stabilized soft-mode materials. Physical review B, 65 (18): 184104. ISSN 1550-235X

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Abstract

We introduce a method for treating soft modes within the analytical framework of the quasiharmonic equation of state. The corresponding double-well energy-displacement relation is fitted to a functional form that is harmonic in both the low- and high-energy limits. Using density-functional calculations and statistical physics, we apply the quasiharmonic methodology to solid periclase (MgO). We predict the existence of a B1-B2 phase transition at high pressures and temperatures.