Devonshire-Landau free energy of BaTiO3 from first principles

Abstract

We have studied the Devonshire-Landau potential underlying the phase transition sequence of BaTiO3 using the first-principles effective Hamiltonian of Zhong, Vanderbilt, and Rabe [Phys. Rev. Lett. 73, 1861 (1994)], which has been very successful in reproducing the phase transitions and the dielectric and piezoelectric properties of this compound. The configuration space (determined by the polarization P as order parameter) was explored with the help of auxiliary electric fields. We show that the typically assumed form of the potential, a sixth-order expansion in P around the paraelectric cubic phase, properly accounts for the behavior of the system, but we find a non-trivial temperature dependence for all the coefficients in the expansion, including the quadratic one, which is shown to behave non-linearly. Our results also prove that the sixth-order terms in the free-energy expansion (needed to account for the first-order character of the transitions and the occurrence of an orthorhombic phase) emerge from an interaction model that only includes terms up to fourth order.

arXiv comment7 pages, two-column style with 11 postscript figures embedded. (Uses RevTeX and epsf macros)

References in corpus (6)

• First-principles theory of ferroelectric phase transitions for perovskites: The case of BaTiO3
• Phase transitions in BaTiO${}_3$ from first principles
• Finite-temperature properties of PZT alloys from first principles
• Lattice dynamics of BaTiO3, PbTiO3 and PbZrO3: a comparative first-principles study
• Ab initio statistical mechanics of the ferroelectric phase transition in PbTiO3
• Electromechanical behavior of BaTiO3 from first principles

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• Ab-initio design of perovskite alloys with predetermined properties: The case of Pb(Sc_{0.5} Nb_{0.5})O_{3}
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• Ab Initio bulk free energy surface of proper ferroelectrics
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