Showing papers by "Sergey Vakhrushev published in 2004"
TL;DR: In this paper, the lattice dynamics for five ordered PbMg supercells were calculated from first principles by the frozen phonon method, and the minimum symmetries of all supercells are reduced by structural instabilities.
Abstract: Lattice dynamics for five ordered ${\mathrm{PbMg}}_{1∕3}{\mathrm{Nb}}_{2∕3}{\mathrm{O}}_{3}$ supercells were calculated from first principles by the frozen phonon method. Maximal symmetries of all supercells are reduced by structural instabilities. Lattice modes corresponding to these instabilities, equilibrium ionic positions, and infrared reflectivity spectra were computed for all supercells. Results are compared with our experimental data for a chemically disordered PMN single crystal.
88 citations
TL;DR: In this article, the lattice dynamics for five ordered PbMg supercells were calculated from first principles by the frozen phonon method, and the minimum symmetries of all supercells are reduced by structural instabilities.
Abstract: Lattice dynamics for five ordered ${\mathrm{PbMg}}_{1∕3}{\mathrm{Nb}}_{2∕3}{\mathrm{O}}_{3}$ supercells were calculated from first principles by the frozen phonon method. Maximal symmetries of all supercells are reduced by structural instabilities. Lattice modes corresponding to these instabilities, equilibrium ionic positions, and infrared reflectivity spectra were computed for all supercells. Results are compared with our experimental data for a chemically disordered PMN single crystal.
83 citations
TL;DR: In the paraelectric phase, the spin-lattice relaxation rate increases with increasing temperature and is much larger than in the bulk phase as mentioned in this paper, due to self-diffusion in the ''premelted state'' induced by microconfinement.
Abstract: Whereas the $^{23}\mathrm{Na}$ spin-lattice relaxation rate ${T}_{1}^{\ensuremath{-}1}$ of microconfined ${\mathrm{NaNO}}_{2}$ in the ferroelectric phase is similar to the one of bulk ${\mathrm{NaNO}}_{2}$, there is a striking difference in the paraelectric phase. Instead of decreasing, the relaxation rate here increases with increasing temperature and is much larger than in the bulk. The difference is due to self-diffusion in the ``premelted state'' induced by microconfinement. This also explains the previously observed giant growth of the dielectric permittivity of confined ${\mathrm{NaNO}}_{2}$ more than 100 K below the melting temperature.
40 citations
TL;DR: In this article, the temperature evolution of the structure of ferroelectric nanowires of NaNO 2 was studied by neutron diffraction from room temperature up to melting, i.e. in ferro-and paraelectric phases.
Abstract: For the first time the temperature evolution of the structure of ferroelectric nanowires of NaNO 2 was studied by neutron diffraction from room temperature up to melting, i.e. in ferro- and paraelectric phases. Samples were produced in natural chrysotile asbestos with average channel diameter 6±1.5 nm. It is demonstrated that in the ferroelectric phase the structure is consistent with the bulk but is strongly textured. The temperature dependence of order parameter in the ferroelectric phase is determined for the confined sodium nitrite. It is shown that this dependence follows a power law with T c =413.0±2.5 K and β =0.34±0.05, and differs from the same for the bulk material.
15 citations
TL;DR: In this paper, high energy resolution neutron spin-echo spectroscopy has been used to measure intrinsic width of diffuse scattering discovered earlier in relaxor ferroelectric crystals and the anisotropic and transverse components of the scattering have been observed in different Brillouin zones.
Abstract: High energy resolution neutron spin-echo spectroscopy has been used to measure intrinsic width of diffuse scattering discovered earlier in relaxor ferroelectric crystals. The anisotropic and transverse components of the scattering have been observed in different Brillouin zones. Both components are found to be elastic within experimental accuracy of 1 eV. Possible physical origin of the static-like behavior is discussed for each diffuse scattering contribution.
1 citations