Competition between rotational and polar structural distortions in perovskites

Autor:	Victor I. Torgashev, A. S. Prokhorov, V. B. Shirokov, L. A. Shuvalov
Rok vydání:	2005
Předmět:	Brillouin zone Physics Phase transition Condensed matter physics Direct sum Irreducible representation Lattice (order) General Materials Science General Chemistry Condensed Matter Physics Landau theory Group theory Phase diagram
Zdroj:	Crystallography Reports. 50:637-645
ISSN:	1562-689X 1063-7745
DOI:	10.1134/1.1996739
Popis:	Symmerically admissible structural distortions are analyzed in terms of the group theory under the assumption that the order parameter is transformed according to the direct sum of irreducible representations M 5 ⊕ R 8 ⊕ Γ10 consisting of the M, R, and Γ points of the Brillouin zone in a primitive cubic lattice. As a result, a set of 92 low-symmetry phases is obtained. The order parameter describes the rotational and polar distortions of the perovskite structure. The topology of the arrangement of the equilibrium phases on phenomenological phase diagrams is considered within the Landau theory of second-order phase transitions. Different variants of the change of the phase states are discussed. The possible existence of several polar states (and their changes) as “final products” of successive structural distortions is substantiated.
Databáze:	OpenAIRE
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