Solid State Vibrational Spectra of Calcium Pyrophosphate Dihydrate

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Department of Chemical Engineering; Department of Chemistry


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 P O 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 P O 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.

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© 1984

Publication Title

Journal of Molecular Structure