Vibrational Spectroscopic Investigation of Phosphate Tetrahedron in Fluor-, Hydroxy-, and Chlorapatites
Yu Liu, ; Comodi, P.; Sassi, P.
published: Oct 20, 1998
ArtNo. ESP154017402005, Price: 29.00 €
Data from infrared and Raman spectra of fluorapatite, hydroxyapatite, and chlorapatite were collected and related to structure data. The spectroscopic data confirm the P63/m space group of the structure of the apatite end-members. A shift of the position of column anions from the mirror plane causes an increase in the distortion of the PO4 tetrahedron both in terms of quadratic elongation and tetrahedral angle variation, and results in a systematical decrease of the stretching frequencies of V1, V3 vibrational modes and a clear increase of splittings of degenerate V3, V4 Raman and infrared active modes. Our results indicate that, on the apatite end-members, the vibrational frequency shift is not a direct consequence of the tetrahedral bond length or volume variation, and the change on values of splitting does not result simply from a dipole-dipole interaction between the phosphate ions in a unit-cell. Therefore there should be a vibrational interaction between the tetrahedron and the structural column.