Investigation of phase transitions in multiferroics HоFe3-xGax(BO3)4 and TbFe3-xGax(BO3)4 solid solution with huntite structure

RFBR funded the reported study according to the research project № 18-02-00754

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)

Raman scattering study of δ-BiB3O6 crystal

The total set of polarized Raman spectra have been obtained at room temperature, and an assignment of observed modes based on the lattice dynamics simulation and polarization selection rules is proposed. An LO-TO splitting of A1 Raman bands have been observed

Anisotropic crystal of the δ-BiB3O6 investigated by vibrational spectroscopy

The vibrational spectroscopy has been applied to investigate the structure the BiB3O6 (BIBO) crystal. Based on the experimental results, the total set of phonons mode of the polarized Raman spectra was proposed. To verify the obtained experimental data have been performed theoretical calculation in software package LADY

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