Peculiarities of the correlation functions, X-ray and neutron scattering in BaTiO{sub 3}

Based on molecular-dynamics (MD) simulations, we have calculated the static and dynamic correlation functions in a BaTiO{sub 3} crystal. The static correlation functions have been used to study the peculiarities of diffuse scattering in barium titanate showing the experimentally observed anomalous p...

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Bibliographic Details
Published inJournal of experimental and theoretical physics Vol. 115; no. 2
Main Authors Matsko, N. L., Maksimov, E. G., Lepeshkin, S. V.
Format Journal Article
LanguageEnglish
Published United States 15.08.2012
Subjects
ABSORPTION SPECTROSCOPY
ATOMIC DISPLACEMENTS
BARIUM COMPOUNDS
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
CORRELATION FUNCTIONS
CRYSTALS
CUBIC LATTICES
DIFFUSE SCATTERING
FINE STRUCTURE
INELASTIC SCATTERING
MOLECULAR DYNAMICS METHOD
NEUTRON DIFFRACTION
OXYGEN IONS
PHASE TRANSFORMATIONS
PHONONS
TIME DEPENDENCE
TITANATES
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY
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Summary:Based on molecular-dynamics (MD) simulations, we have calculated the static and dynamic correlation functions in a BaTiO{sub 3} crystal. The static correlation functions have been used to study the peculiarities of diffuse scattering in barium titanate showing the experimentally observed anomalous planes. Based on time-dependent pair correlation functions, we have calculated the phonon spectra of BaTiO{sub 3} and studied the central peak of inelastic scattering. The phonon frequencies calculated by the MD method agree well with those obtained previously in the quasi-harmonic approximation. We show that the central peak of inelastic scattering is associated mainly with the soft optic mode and has the same symmetry. The large anisotropy in the displacements of atoms in the soft mode allows the presence of peculiarities in both X-ray scattering and EXAFS spectroscopy to be explained. The characteristic shape of the EXAFS spectra is shown to be explained by the quasi-one-dimensional motion of the oxygen ions in the cubic lattice of BaTiO{sub 3}. Our calculation of triple correlation functions shows that the titanium atom in the described model oscillates around the cubic cell center. Explaining the experimental data that have caused disagreement about the nature of the phase transition in BaTiO{sub 3} using the developed model gives grounds to treat the phase transition in barium titanate as a displacive one.
ISSN:1063-7761
1090-6509
DOI:10.1134/S1063776112070102