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Type: Artigo de periódico
Title: Light Scattering From Batio3: The Clg Model
Author: Ozorio De Almeida A.M.
Abstract: The model proposed by Comes, Lambert and Guinier (1968) (hereafter called CLG) for all but the lowest phase of BaTiO3 assumes that each Ti atom has more than one possible equilibrium position, but that their configurations in neighbouring cells are such as to form long linear domains. In the limit of infinitely long chains this disorder is static. The harmonic approximation of the movement of the atoms around their disorder configuration leads to the existence of some modes that are identical to the modes of the averaged lattice. These include all the usually Raman active modes in ordered crystals and it is shown that in the present case these same modes account for perfect coherent scattering from all the cells in the crystal. Contrary to the ordered material, however, the CLG crystal can also scatter incoherently from single cells or from whole chains, leading to a diffuse background spectrum. Major features in the spectra of tetragonal BaTiO3 are thus accounted for, but measurements taken just above the ferroelectric transition temperature seem to suggest that in this region the disposition of parallel chains is correlated.
Rights: fechado
Identifier DOI: 10.1088/0022-3719/11/20/008
Date Issue: 1978
Appears in Collections:Unicamp - Artigos e Outros Documentos

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