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| Hauptseite > Publikationsdatenbank > Lattice dynamics of rhenium trioxide from the quasiharmonic approximation |
| Hauptseite > Publikationsdatenbank > Lattice dynamics of rhenium trioxide from the quasiharmonic approximation |
| Journal Article | PreJuSER-11953 |
; ; ; ;
2010
APS
College Park, Md.
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Please use a persistent id in citations: http://hdl.handle.net/2128/10967 doi:10.1103/PhysRevB.82.104301
Abstract: The quasiharmonic theory is applied to study the lattice dynamics and thermal properties of rhenium trioxide, a material exhibiting the negative thermal-expansion phenomenon. Phonons are calculated at several external pressures. The pressure dependence of the M, R, and zone-center phonon modes is analyzed. Relying on the Gruneisen formalism an influence of temperature on the M phonon mode is investigated. The calculated free energy of the system provides predictions for the temperature dependence of such quantities as equilibrium volume and crystal thermal expansivity. The mean-squared vibrations of rhenium-trioxide atoms are investigated versus temperature and pressure. Results of the calculations indicate a softening of the M and R phonons with pressure and a large negative Gruneisen constants for these modes. A decrease in the crystal volume is observed up to 170 K. The thermal-expansion coefficient shows a minimum in the vicinity of 100 K which corresponds to a minimum of the anisotropy in the oxygen thermal vibrations perpendicular to the Re-O bond and along the bond. Anisotropy in the oxygen Debye-Waller factors follows from the anisotropy of the force constants at the oxygen site. Inelastic neutron-scattering measurements performed at room temperature are reported together with the generalized phonon densities of states. A comparison between present calculations and the experimental data as well as other theoretical studies is provided.
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