Vibrational spectra of double diphosphates RbLnP 2O 7 (Ln = Dy, Ho, Y, Er, Tm, Yb)

Abstract

The rubidium double diphosphates RbLnP 2O 7 (Ln=Dy, Ho, Y, Er, Tm, Yb) have been conjointly studied by X-ray diffraction and vibrational spectroscopy. The infrared and Raman spectra of these compounds were established and interpreted using factor group analysis. The spectral features predicted with factor group arising from the X-ray crystallographic space group P2 1 / c (C 2h 5) for these compounds fit the observed results. The similarities between the vibrational spectra of RbLnP 2O 7 show that they are isostructural. Non-coincidences are observed between most infrared and Raman bands confirm a centrosymetric structure for these compounds. The vibrational spectra point to a bent POP bridge angle in all these materials. The slight shift of the frequencies of ν as(POP) and ν s(POP) on the vibrational spectra is due to the influence of the cation Ln 3+ on the POP bridge angle. The POP angle values were estimated using the Lazarev’s relationship.