Vibrational spectra of synthetic crandallite-type minerals—optical and inelastic neutron scattering spectra

✍ Scribed by D. K. Breitinger; G. Brehm; J. Mohr; D. Colognesi; S. F. Parker; A. Stolle; Th. H. Pimpl; R. G. Schwab

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 195 KB
• Volume: 37
• Category: Article
• ISSN: 0377-0486
• DOI: 10.1002/jrs.1444

✦ Synopsis

Abstract

The vibrational spectra of the synthetic minerals crandallite and goyazite MAl~3~(OH)~6~(HPO~4~)(PO~4~) (M = Ca and Sr) were studied by means of vibrational (IR and Raman) and inelastic neutron scattering (INS) spectrometries at room and low temperatures. The results were discussed taking into consideration the effects of different types of disorder (random distribution of PO~4~ and HPO~4~, orientational distribution with HPO~4~ and displacement of Ca in crandallite). The consequences of the resulting perturbed symmetry and of the non‐equivalence of the bridging µ‐OH groups in the Al~2~OH fragments were pointed out (complexity of the ν(Al~2~OH), δ(Al~2~OH) and γ(Al~2~OH) bands). The vibrations of the PO~4~ and HPO~4~ groups could be separated. Some aspects of the vibrational behaviour of the AlO~2~(OH)~4~ units and of the layers composed therewith were addressed. The translational modes of the interlayer cations Ca^2+^ and Sr^2+^ could be observed; the findings support the suggested displacement of Ca in crandallite. Copyright © 2006 John Wiley & Sons, Ltd.