Publication
The experimentally observed temperature dependence of the quartic coefficients in the Landau-Devonshire expansion for BaTiO3 is naturally accounted for within a proper fluctuation model. It is explained, in particular, why one of the quartic coefficients varies with temperature above T-c, while the second is constant. It is argued that the tetragonal phase in BaTiO3 exists essentially due to thermal fluctuations, while the true Landau-Devonshire expansion with temperature-independent coefficients favors the rhombohedral ferroelectric phase. (C) 2002 MAIK "Nauka / Interperiodica".
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