CENTROSYMMETRIC PEROVSKITE CRYSTAL STRUCTURES WITH SPACE GROUP Pbnm: CRYSTALLOGRAPHIC PARAMETERIZATION OF KCaF3 BETWEEN 100 AND 400 K IN TERMS OF THE AMPLITUDES OF SYMMETRY-ADAPTED BASIS VECTORS OF THE CUBIC ARISTOTYPE PHASE

摘要: The crystal structures of centrosymmetric, zone-boundary-tilted perovskite-structured phases with space group Pbnm can be decomposed in terms an appropriate set symmetry-adapted basis vectors, for irreducible representations wave vectors on the surface Brillouin zone cubic aristotype phase. Such a decomposition potentially allows physical to derived any observed structural distortion (bond lengths, bond angles, polyhedron volumes) as function applied thermodynamic variable (temperature, pressure, magnetic or electric field), indeed chemical composition studies solid solutions. methodology is illustrated using results from parametric study temperature dependence structure KCaF 3 between 100 and 400 K.