Vibrational spectrum of KMIIP3O9 tricyclophosphates with the benitoite structure

The Raman and i.r. spectra of tricyclophosphates KMIIP3O9 (MII = Mg, Ca, Co, Mn, Zn, Cd) with the benitoite structure are discussed on the basis of a factor group analysis, and by comparison with the spectrum of the structurally related LaP3O9. 3 H2O. Most of the stretching frequencies have been observed and assigned, whereas the assignment of the bending modes remains more or less hypothetical. Low-frequency i.r. bands have been assigned to translations of either K or MII cations on the basis of mass effects. The influence of the ring chain polymorphism is briefly discussed. © 1987.