Raman spectroscopy study of the switchable phases metal-organic frameworks DUT-8(Ni)

Acknowledgments: I.S.,V.B., S.K. thank the DFG for financial support (FOR 2433); A.K., S.K., A.V. thank the Russian Foundation for Basic Research for financial support (18-02-00754)

Cubic to cubic phase transition in (NH4)3SnF7 ferroelastic crystal – Raman scattering study

This work was supported by Russian Foundation for Basic Research (Grant N 17-02-00920)

Nature of phase transitions in ammonium oxofluorovanadates, a vibrational spectroscopy study of (NH4)3VO2F4 and (NH4)3VOF5

Two ammonium oxofluorovanadates, (NH4)3VO2F4 and (NH4)3VOF5, have been in-vestigated by temperature-dependent infrared and Raman spectroscopy methods to determine the nature of phase transitions (PT) in these compounds. Dynamics of quasioctahedral groups was simulated within the framework of semi-empirical approach, which justified the cis-conformation of VO2F43– (C2v) and the C4v geometry of VOF53–. The observed infrared and Raman spectra of both compounds at room temperature (RT) revealed the presence at least of two crystallographically independent octahedral groups. The first order PT at elevated temperatures is connected with a complete dynamic disordering of these groups with only single octahedral state. At lower temperatures, the octahedra are ordered and several octahedral states appear. This PT is the most pronounced in the case of (NH4)3VOF5, when at least seven independent VOF53– octahedra are present in the structure below 50 K, in accordance with the Raman spec-tra. Ammonium groups do not take part in PTs at higher and room temperatures but their reorientational motion freezes at lower temperatures

Magnon mode in α‐MnS Raman spectrum

Представлены спектры комбинационного рассеяния моносульфида марганца (α‐MnS) со структурой NaCl в температурном интервале 5–300 К. При низких темпепературах обнаружен новый пик 22 cm–1. Температурная зависимость этого пика позволяет отнести его к магнонной моде при k = 0. Это хорошо согласуется с волновым числом магнона, рассчитанного с использованием программного пакета Munich SPRKKR

Polarized Raman spectroscopy of delta-BiB3O6 at 7–350 K

BiB3O6 crystal has been characterized by Raman spectroscopy. Polarized low-frequency spectra have been obtained. Temperature measurements have been carried out in range 7–350 K. Raman spectra have been numerically simulated with lady software package. The results of experiment confirmed the contribution of the Bi3+ ions and BO4 groups in nonlinear optical properties of BiB3O6. The studied crystal is a promising medium for up- and down-Raman laser-frequency converters

Polarized Raman spectroscopy of delta-BiB3O6 at 7–350 K

BiB3O6 crystal has been characterized by Raman spectroscopy. Polarized low-frequency spectra have been obtained. Temperature measurements have been carried out in range 7–350 K. Raman spectra have been numerically simulated with lady software package. The results of experiment confirmed the contribution of the Bi3+ ions and BO4 groups in nonlinear optical properties of BiB3O6. The studied crystal is a promising medium for up- and down-Raman laser-frequency converters