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1.
A. N. Vtyurin A. S. Krylov S. V. Goryainov S. N. Krylova A. S. Oreshonkov V. N. Voronov 《Physics of the Solid State》2012,54(5):934-936
The Raman spectra of the elpasolite (Rb2KInF6) crystal have been studied in the pressure range from 0 to 5.3 GPa at a temperature of 295 K. A phase transition at a pressure of approximately 0.9 GPa has been found. An analysis of the variations in the spectral parameters has led to the conclusion that the phase transition to a distorted phase is accompanied by the doubling of the volume of the primitive cell of the initial cubic phase. Numerical calculations of the lattice dynamics in the Rb2KInF6 crystal have been performed. The numerical simulation has established that the phase transition at a pressure of 0.9 GPa is associated with condensation of the F lg mode. A probable high-pressure phase is the phase with space group C2/m. 相似文献
2.
Optics and Spectroscopy - The Raman spectra of an Rb2KLuF6 crystal are studied in the temperature range from 8 to 375 K, which includes two phase transitions: one of which proceeds from a cubic to... 相似文献
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Sergei V. Goryainov Alexander S. Krylov Yuanming Pan Iliya A. Madyukov Mikhail B. Smirnov Alexander N. Vtyurin 《Journal of Raman spectroscopy : JRS》2012,43(3):439-447
Layer silicates F‐ and OH‐apophyllites, KCa4Si8O20(F, OH)·8H2O, have been investigated by Raman spectroscopy at hydrostatic and nonhydrostatic pressures up to ~8 GPa in diamond anvil cells using a 4 : 1 methanol–ethanol mix as pressure‐transmitting medium. Our experiments show that at hydrostatic compression, apophyllites retain their crystalline states (i.e. no amorphization) up to 5 GPa. The wavenumbers of most bands exhibit linear dependences on pressure, except for a few ones, e.g. at 162 and 3565 cm–1 in OH‐form (160.5 and 3558 cm–1 in F‐form) that show nonlinear dependences. Nonhydrostatic compression with additional uniaxial loading induces amorphization of apophyllites. The majority of the bands in OH‐apophyllite decreases markedly in intensity and shows considerable broadening under nonhydrostatic compression up to 3–6 GPa. In addition, the wavenumbers of several bands at nonhydrostatic compression exhibit considerable nonlinear dependences on pressure with strong hysteresis. These bands are mainly associated with vibrations of the interlayer ions and molecules and also of stretching and bending silicate sheets, hence being highly sensitive to the interlayer distance. Finally, we have calculated the lattice dynamics of F‐apophyllite and interpreted the majority of bands, and these data are used to explain the complex baric behavior of the bands. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
4.
A. N. Vtyurin A. Bulou A. S. Krylov M. L. Afanas’ev A. P. Shebanin 《Physics of the Solid State》2001,43(12):2307-2310
This paper reports on a Raman study of the cubic-to-monoclinic phase transition in (NH4)3ScF6 cryolite. We observed sharp anomalies in the frequencies and half-widths of the Raman lines corresponding to internal vibrations of the ScF 6 3+ ions and to lattice vibrations; no soft lattice mode condensation was revealed. It is concluded that the phase transition studied is related primarily to the orientational ordering of these ions. 相似文献
5.
Yu. V. Gerasimova A. S. Krylov A. N. Vtyurin N. M. Laptash S. V. Goryaĭnov 《Physics of the Solid State》2008,50(8):1534-1537
Raman spectra of a polycrystalline sample of the perovskite-like oxyfluoride (NH4)3TiOF5 are measured in the frequency region 100–3600 cm?1 at temperatures ranging from 91 to 370 K under hydrostatic pressures of up to 9 GPa, which include the range of the phase transition from the orientationally disordered cubic phase to the low-symmetry phase. Anomalies in the spectral parameters due to the phase transition are revealed in the range of vibrations of TiOF5 octahedral groups. 相似文献
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K. S. Aleksandrov V. N. Voronov A. N. Vtyurin S. V. Goryainov N. G. Zamkova V. I. Zinenko A. S. Krylov 《Journal of Experimental and Theoretical Physics》2002,94(5):977-984
New phase transitions induced by hydrostatic pressure in a cubic (under standard conditions) ScF3 crystal are discovered by the methods of polarization microscopy and Raman scattering. The space groups $R\bar 3c$ for Z=2 and Pnma for Z=4 are proposed for the high-pressure phases. A nonempirical computation of the lattice dynamics of the crystal is carried out. It is shown that, under normal pressure, the cubic phase is stable down to T=0 K, while the application of a hydrostatic pressure gives rise to a phonon branch in the vibrational spectrum (between points R and M of the Brillouin zone) with negative values of squares of frequencies. The condensation of soft mode R5 at the boundary point of the Brillouin zone leads to rhombohedral distortion of the cubic structure with the unit cell volume doubling. The calculated frequencies at q=0 of the ScF3 lattice in the distorted rhombohedral phase are real-valued; the number and position of frequencies active in Raman scattering are in accord with the experimental values. 相似文献
8.
A. N. Vtyurin A. S. Krylov S. V. Goryaĭnov S. N. Krylova V. N. Voronov 《Physics of the Solid State》2006,48(6):1070-1072
The Raman spectra of Rb2KScF6 elpasolite crystals are studied in the pressure range up to 7 GPa. A phase transition is revealed at a pressure of approximately 1 GPa. Analysis of the changes in the spectral parameters shows that the phase transition is accompanied by a doubling of the volume of the primitive cell in the initial cubic phase. Judging from the character of the variations in the pressure dependences of the frequency of the observed vibrations, there can exist another transition to the phase with a lower symmetry at a pressure of approximately 2.1 GPa. 相似文献
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K. S. Aleksandrov A. N. Vtyurin I. V. Shmygol’ S. V. Goryainov 《Physics of the Solid State》1999,41(9):1541-1543
Using polarization microscopy and Raman scattering, we have discovered a new phase transition in the layered perovskite crystal
CsScF4 under a hydrostatic pressure around 6 GPa. The proposed space group of the high-pressure phase is C
2h
2
, Z=4.
Fiz. Tverd. Tela (St. Petersburg) 41, 1683–1685 (September 1999) 相似文献