Vibrational spectroscopy and x-ray diffraction ofCd(OH)2to28G

Abstract

We report Raman and infrared absorption spectroscopy along with X-ray diffraction for brucitetype β-Cd(OH) 2 to 28 GPa at 300 K. The OH-stretching modes soften with pressure and disappear at 21 GPa with their widths increasing rapidly above 5 GPa, consistent with a gradual disordering of the H sublattice at 5-20 GPa similar to that previously observed for Co(OH) 2 . Asymmetry in the peak shapes of the OH-stretching modes suggests the existence of diverse disordered sites for H atoms in Cd(OH) 2 under pressure. Above 15 GPa, the A 1g (T) lattice mode shows nonlinear behavior and softens to 21 GPa, at which pressure significant changes are observed: new Raman modes appear, two Raman-active lattice modes and the OH-stretching modes of the lowpressure phase disappears, and the positions of some X-ray diffraction lines change abruptly with the appearance of weak new diffraction features. These observations suggest that amorphization of the H sublattice is accompanied by a crystalline-to-crystalline transition at 21 GPa in Cd(OH) 2 , which has not been previously observed in the brucite-type hydroxides. The Raman spectra of the high-pressure phase of Cd(OH) 2 is similar to those of the high-pressure phase of single-crystal Ca(OH) 2 of which structure has been tentatively assigned to the Sr(OH) 2 type.2

High‐Temperature Vibrational Spectra Between Mg (OH)2 and Mg (OD)2: Anharmonic Contribution to Thermodynamics and D/H Fractionation for Brucite

“…While Kruger et al (1989) also observed a pressure dependence of −0.6 cm −1 /GPa for the IR-active OH stretching mode, by high-pressure FTIR experiment on Mg (OH) 2 up to 30 GPa. Similar negative pressure dependence for the internal OH stretching modes have also been observed in other brucite-type minerals, such as Ca (OH) 2 (Kruger et al, 1989), β-Ni (OH) 2 (Murli et al, 2001), Co (OD) 2 (Shieh & Duffy, 2002), Fe (OH) 2 (Speziale et al, 2005), and Cd (OH) 2 (Shim et al, 2006).…”

Optoelectronic properties and temperature dependent mechanisms of composite-hydroxide-mediated approach for the synthesis of CdO nanomaterials

“…Its low intensity and large width are consistent with expectations for the vibration mode (E g (R)) and tentatively has assigned to the vibrational mode of Cd (OH) 2 . [23] Our Raman analysis provides significance of the growth temperature for size manipulation and subsequent effect on the Raman spectra of CdO nano product.…”

Raman and infrared spectral studies of [C(NH2)3]2MII(H2O)4(SO4)2, MII = Mn, Cd and VO

“…Four corners of each octahedron are occupied by water molecules, and the remaining two apices by the oxygen atoms belonging to sulfate groups. 20 This may lead to the formation of SO 4 tetrahedra with relatively longer and shorter S-O bond lengths in the structure coordinated with CdO 6 octahedra. The guanidinium groups are located above and below these layers.…”

“…Hydrogen bonds from the water molecules connect these clusters to form layers. 20,21 The sulfate group with its T d symmetry usually has S-O bond lengths around 1.47Å and O-S-O angles around 109°in its free state. One corner of each tetrahedron points away from the layer, since no hydrogen bonding from this oxygen atom to the O-H groups within the layer is possible.…”