Solid state vibrational spectra of calcium pyrophosphate dihydrate

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The Raman and IR spectra of triclinic Ca2P2O7 2H2O are interpreted using factor group analysis. Solid state effects, factor group splitting and two-site splitting, must be considered to explain the spectra; site group or free ion group models are inadequate. The simple unit cell of this pyrophosphate allows unambiguous assignment of the eight PO stretching modes in order of decreasing energy: 4 vaPO > vsPO > vaPO > vaPOP > vsPOP. Comparison of these spectra with those for pyrophosphates exhibiting larger unit cells demonstrates that the number of factor group split symmetric PO stretching modes, vsPO, in the Raman spectra is proportional to the unit cell size. These spectra uniquely characterize this medically interesting material which can cause in vivo crystal-induced inflammation in tissues. © 1984.

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Journal of Molecular Structure