Physics – Condensed Matter – Materials Science
Scientific paper
2000-09-27
Physics
Condensed Matter
Materials Science
7 pages, two-column style with 11 postscript figures embedded. (Uses RevTeX and epsf macros)
Scientific paper
10.1103/PhysRevB.63.144103
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.
Garcia Alberto
Íñiguez Jorge
Ivantchev S.
Perez-Mato Juan Manuel
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