Room temperature single-crystal diffuse scattering and ab initio lattice dynamics in CaTiSiO5

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DOIResolve DOI: http://doi.org/10.1088/0953-8984/25/31/315402
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TypeArticle
Journal titleJournal of Physics Condensed Matter
ISSN0953-8984
Volume25
Issue31
Article number315402
SubjectAnti ferroelectrics; Density-functional perturbation theory; Diffuse scattering; High energy X ray; Phonon dispersion curves; Phonon dispersions; Scattering pattern; Static displacement; Acoustic dispersion; Ferroelectric materials; Lattice vibrations; Phonons; Solids; Strain measurement; Scattering
AbstractSingle-crystal diffuse scattering data have been collected at room temperature on synthetic titanite using both neutrons and high-energy x-rays. A simple ball-and-springs model reproduces the observed diffuse scattering well, confirming its origin to be primarily due to thermal motion of the atoms. Ab initio phonons are calculated using density-functional perturbation theory and are shown to reproduce the experimental diffuse scattering. The observed diffuse x-ray and neutron scattering patterns are consistent with a summation of mode frequencies and displacement eigenvectors associated with the entire phonon spectrum, rather than with a simple, short-range static displacement. A band gap is observed between 600 and 700 cm-1 with only two modes crossing this region, both associated with antiferroelectric Ti-O motion along a. One of these modes (of B u symmetry), displays a large LO-TO mode-splitting (562-701.4 cm-1) and has a dominant component coming from Ti-O bond-stretching and, thus, the mode-splitting is related to the polarizability of the Ti-O bonds along the chain direction. Similar mode-splitting is observed in piezo- and ferroelectric materials. The calculated phonon dispersion model may be of use to others in future to understand the phase transition at higher temperatures, as well as in the interpretation of measured phonon dispersion curves. © 2013 IOP Publishing Ltd.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); NRC Canadian Neutron Beam Centre (CNBC-CCFN)
Peer reviewedYes
NPARC number21269583
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Record identifierefa0fc1f-8755-4ae2-b2de-e4d3df4bc5b6
Record created2013-12-13
Record modified2016-05-09
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