Temperature and pressure dependence of Raman-active phonons of CaMoO4: An anharmonicity study

Sarantopoulou, E; Raptis, C; Ves, S; Christofilos, D; Kourouklis, GA

dc.contributor.author	Sarantopoulou, E	en
dc.contributor.author	Raptis, C	en
dc.contributor.author	Ves, S	en
dc.contributor.author	Christofilos, D	en
dc.contributor.author	Kourouklis, GA	en
dc.date.accessioned	2014-03-01T01:18:24Z
dc.date.available	2014-03-01T01:18:24Z
dc.date.issued	2002	en
dc.identifier.issn	0953-8984	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/14980
dc.subject.classification	Physics, Condensed Matter	en
dc.subject.other	Chemical bonds	en
dc.subject.other	Crystal atomic structure	en
dc.subject.other	Crystal lattices	en
dc.subject.other	Lattice vibrations	en
dc.subject.other	Phonons	en
dc.subject.other	Pressure effects	en
dc.subject.other	Raman scattering	en
dc.subject.other	Spectrum analysis	en
dc.subject.other	Thermal effects	en
dc.subject.other	Anharmonicity analysis	en
dc.subject.other	Ionic bonds	en
dc.subject.other	Calcium compounds	en
dc.title	Temperature and pressure dependence of Raman-active phonons of CaMoO4: An anharmonicity study	en
heal.type	journalArticle	en
heal.identifier.primary	10.1088/0953-8984/14/39/302	en
heal.identifier.secondary	http://dx.doi.org/10.1088/0953-8984/14/39/302	en
heal.language	English	en
heal.publicationDate	2002	en
heal.abstract	The Raman spectra of tetragonal CaMoO4 (scheelite structure, C-4h(6) space group) have been measured in the temperature range 12-1300K. At high temperatures, the frequency and linewidth of all Raman-active phonons vary almost linearly with temperature, indicating that the three-phonon decay processes are dominant over the four-phonon ones. All Raman phonons display normal negative (partial derivativeomega/partial derivativeT) slopes throughout the temperature range, except for the lowest-frequency B-g phonon at 111.5 cm(-1) which is almost temperature independent in the region 12-400 K, but then for T > 400 K it shows a slight (normal) softening with temperature. The reduced (partial derivativeomega/partial derivativeT)/omega slopes of the internal modes (vibrations of atoms within the tetrahedral MoO42- units) are an order of magnitude smaller than the respective slopes of the external ones (pure lattice modes). There are no discontinuities or sharp changes of slope in the omega (T) plots, implying that CaMoO4 remains stable over the entire temperature range. Combining the temperature-dependent Raman data of this work and the previously reported pressure-dependent Raman data on this crystal (Christofilos D, Kourouklis G A and Ves S 1995 J. Phys. Chem. Solids 56 1125), as well as the thermal expansion coefficient (T) and compressibility kappa (T) data, it has been possible to separate and evaluate quantitatively the volume (expansion) Deltaomega(vol) and the pure temperature (anharmonic) Deltaomega(anh) contributions to the total Deltaomega(tot) shift of phonons with temperature. It has been found that for most phonons at high temperatures, the volume effect is greater than the pure temperature one, thus indicating that most of the bonds in CaMoO4 are predominantly ionic in character.	en
heal.publisher	IOP PUBLISHING LTD	en
heal.journalName	Journal of Physics Condensed Matter	en
dc.identifier.doi	10.1088/0953-8984/14/39/302	en
dc.identifier.isi	ISI:000178910500008	en
dc.identifier.volume	14	en
dc.identifier.issue	39	en
dc.identifier.spage	8925	en
dc.identifier.epage	8938	en