Vibrational spectroscopy of the borate mineral henmilite Ca₂Cu[B(OH)₄]₂(OH)₄.
Henmilite is a triclinic mineral with the crystal structure consisting of isolated B(OH)(4) tetrahedra, planar Cu(OH)(4) groups and Ca(OH)(3) polyhedra. The structure can also be viewed as having dimers of Ca polyhedra connected to each other through 2B(OH) tetrahedra to form chains parallel to the C axis. The structure of the mineral has been assessed by the combination of Raman and infrared spectra. Raman bands at 902, 922, 951, and 984 cm(-1) and infrared bands at 912, 955 and 998 cm(-1) are assigned to stretching vibrations of tetragonal boron. The Raman band at 758 cm(-1) is assigned to the symmetric stretching mode of tetrahedral boron. The series of bands in the 400-600 cm(-1) region are due to the out-of-plane bending modes of tetrahedral boron. Two very sharp Raman bands are observed at 3559 and 3609 cm(-1). Two infrared bands are found at 3558 and 3607 cm(-1). These bands are assigned to the OH stretching vibrations of the OH units in henmilite. A series of Raman bands are observed at 3195, 3269, 3328, 3396, 3424 and 3501 cm(-1) are assigned to water stretching modes. Infrared spectroscopy also identified water and OH units in the henmilite structure. It is proposed that water is involved in the structure of henmilite. Hydrogen bond distances based upon the OH stretching vibrations using a Libowitzky equation were calculated. The number and variation of water hydrogen bond distances are important for the stability off the mineral.
Effect of B2O3 content on Eu3+−Surrounding in the system SrO−x.B2O3 containing Eu3+ ions prepared by combustion method
Abstract The change of Eu3+− surrounding in the system SrO−x.B2O3 with various x values (x = 0.33, 0.5, 1) synthesized by combustion method was investigated via photoluminescence (PL) spectra and phonon sideband (PSB) spectra. From the analysis of PSB spectra, it is reasonable to suggest that when increasing B2O3 content the electron−phonon coupling strength increases due to the increase in the number of B O− non−bridging bond. By using Judd−Ofelt (JO) theory for PL spectra of Eu3+ ion, the Ω2 intensity parameter was calculated and it also shows the asymmetry of Eu3+− surrounding increase corresponding to the B2O3 content.
Uncoupled HDO Modes Caused by Metal Guest Ions in Crystal Matrices
The stretching frequencies of HDO molecules isolated in solid hydrates (isotopically dilute samples) are an excellent probe of the local potential of the water molecules. Unfortunately interpretation of the uncoupled 0H(0D) modes obtained in this way is complicated by the fact that one single parameter, namely the shift of the frequencies relative to those of gaseous HDO, represents a lot of different effects, as strength of H-bond acceptor groups, anharmonicity of the OH(OD) vibrations, repulsion potential of the lattice, distances to the acceptor groups, and metal oxygen interaction (M… OH2).