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91.
V. D. Fokina I. N. Flerov M. S. Molokeev E. I. Pogorel’tsev E. V. Bogdanov A. S. Krylov A. F. Bovina V. N. Voronov N. M. Laptash 《Physics of the Solid State》2008,50(11):2175-2183
Elpasolite Rb2KTiOF5 (space group, Fm $ \bar 3 Elpasolite Rb2KTiOF5 (space group, Fm
m, Z = 4) was synthesized using a solid-phase reaction method. The temperature dependences of the heat capacity, the unit cell
parameters, the structure, the permittivity, the response to an external pressure, and the Raman spectra were studied. A nonferroelectric
phase transition was revealed at T
0 = 215 K; the transition is accompanied by a tetragonal distortion of the unit cell (space group I4/m, Z = 10) and a change in the entropy (ΔS
0 = Rln8), which is anomalously large for perovskite-like oxyfluorides with atomic cations. The specific features of the mechanism
of structure distortion are discussed in combination with the previous experimental data obtained for cryolite (NH4)3TiOF5 and elpasolite Rb2KGaF6.
Original Russian Text ? V.D. Fokina, I.N. Flerov, M.S. Molokeev, E.I. Pogorel’tsev, E.V. Bogdanov, A.S. Krylov, A.F. Bovina,
V.N. Voronov, N.M. Laptash, 2008, published in Fizika Tverdogo Tela, 2008, Vol. 50, No. 11, pp. 2084–2092. 相似文献
92.
V. D. Fokina E. V. Bogdanov M. V. Gorev M. S. Molokeev E. I. Pogorel’tsev I. N. Flerov N. M. Laptash 《Physics of the Solid State》2010,52(4):781-788
The thermal and dielectric properties of the (NH4)2NbOF5 oxyfluoride have been investigated. It has been established that the structural phase transitions Cmc21 → C2 → Ia observed at the temperatures T
1 = 258.0 K and T
2 = 218.9 K exhibit a nonferroelectric nature. The hydrostatic pressure, which stabilizes the initial phase and destabilizes
the low-temperature phase, hardly affects the temperature range of stability of the intermediate phase. The model of sequential
ordering of the structural elements due to phase transitions has been analyzed using experimental data on the entropies of
the phase transitions. 相似文献
93.
E. A. Mikhaleva I. N. Flerov A. V. Kartashev M. V. Gorev M. S. Molokeev L. N. Korotkov E. Rysiakiewicz-Pasek 《Physics of the Solid State》2018,60(7):1338-1343
The effect of restricted geometry on specific heat capacity and thermal expansion of the triglycine sulfate (TGS)–borosilicate glass composites have been studied first. A decrease in the entropy and temperature of the P21 ? P21/m phase transition in the TGS component with decreasing the glass matrix pore diameter at the invariable specific heat and thermal expansion coefficient has been observed. The estimates are indicative of the minor effect of internal pressure on the TGS pressure coefficient dTC/dp in the composites. 相似文献
94.
Two salts and the salt cocrystal of ciprofloxacin with thiobarbituric and barbituric acids: The structure and properties 下载免费PDF全文
Nicolay N. Golovnev Maxim S. Molokeev Maxim K. Lesnikov Victor V. Atuchin 《Journal of Physical Organic Chemistry》2018,31(3)
Ciprofloxacin (CfH, C17H18FN3O3) crystallizes with 2‐thiobarbituric (H2tba) and barbituric acid (H2ba) in the aqueous solution to yield salt CfH2(Htba)·3H2O ( 1 ), salt cocrystal CfH2(Hba)(H2ba)·3H2O ( 2 ), and salt CfH2(Hba)·H2O ( 3 ). The compounds are structurally characterized by the X‐ray single‐crystal diffraction. The numerous intermolecular hydrogen bonds N–H?O and O–H?O formed by water molecules, Htba?/Hba? and CfH2+ ions, and H2ba molecules stabilize the crystal structures of 1 to 3 . Hydrogen bonds form a 2D plane network in the salts of 1 and 3 and a 3D network in the salt cocrystal of 2 . There are different π‐π interactions in 1 to 3 . The compounds have been characterized by powder X‐ray diffraction, thermogravimetry/differential scanning calorimetry, and Fourier transform infrared spectroscopy. The compounds dehydration ends at 130°C to 150°C, and their oxidative decomposition is observed in the range of 250°C to 275°C. 相似文献
95.
Denisova L. T. Molokeev M. S. Chumilina L. G. Ryabov V. V. Denisov V. M. 《Physics of the Solid State》2021,63(4):534-537
Physics of the Solid State - Titanate GdGaTi2O7 has been obtained from the initial oxides Gd2O3, Ga2O3, and TiO2 by the solid-state synthesis via annealing in air at temperatures of 1273 and 1573... 相似文献