Vibrational Study, Reinvestigation of the Crystal Structure of MgHPO4.3H2O and Calculated IR Frequencies for the PO43- by Isotopic Substitutions

Abstract

The monohydrogenomonophosphatetrihydrate of magnesium MgHPO4.3H2O was reinvestigated by X-ray diffraction, vibrational spectroscopy, nuclear magnetic resonance and calculation of the IR frequencies by using isotopic substitutions. MgHPO4.3H2O is orthorhombic, space group Pbca with the following unit-cell parameters: a = 10.0133(2) Å, b= 10.2136(1) Å, c =10.6853(2) Å, Z = 8 and V = 1092.81(3) Å3. Raman and infrared spectra of MgHPO4.3H2O have been recorded and interpreted on the basis of factor group analysis. The occurrence of the four frequencies ν1, v2, v3, v4 in the vibrational spectra confirms the existence of the PO43− tetrahedron.