Landau-devonshire theory with rotationally invariant expansion coefficients

Abstract

Abstract General expressions pertaining to a centrosymmetric prototype phase are given for the correction terms to the third and fourth order expansion coefficients of the Landau-Devonshire free energy with respect to the displacement gradient and the polarization, that arise as a consequence of the rotational invariance condition. Application to crystals of Oh symmetry shows that the correction terms may be numerically significant.