The vibrational spectra of α-alkaline earth pyrophosphates

Raman spectra and middle infrared absorption spectra (4000-200 cm-1) were measured for α-Ca2P2O7, α-Sr2P2O7, and α-Ba2P2O7. These spectra were interpreted using factor group analyses, and band assignments were made. Noncoincidences in the infrared and Raman spectra of α-Sr2P2O7 indicated that this material possesses the centrosymmetric space group D162h-Pnma rather than the noncentrosymmetric space group, C92ν-Pna21. The similarities between the vibrational spectra of α-Ba2P2O7 and α-Sr2P2O7 suggested that α-Ba2P2O7 is isostructural with α-Sr2P2O7. Differences were noted in the vibrational spectra of monoclinic α-Ca2P2O7 and the two orthorhombic α-phases, α-Sr2P2O7 and α-Ba2P2O7, which were related to differences in their crystal structures. The P2O74--anions of all three compounds contained nonlinear POP bond angles. © 1978

The vibrational spectra and normal coordinate analysis of \u3c sup\u3e 28 \u3c/sup\u3e SI — and \u3c sup\u3e 29 \u3c/sup\u3e SI — substituted α-cristobalite

Infrared and Raman spectra were measured for 28Si- and 29Si-substituted α-cristobalite. The spectra were analyzed by normal coordinate analysis using a modified valence force field. The resulting force constants were consistent with those calculated for related SiO2-containing phases. © 1985, Taylor & Francis Group, LLC. All rights reserved