The vibrational spectra and structures of rare earth oxides in the A modification

Abstract

Crystallographic studies of La2O3 and the oxides isostructural with it have failed to decide between noncentrosymmetric space group D32(P321) and the centrosymmetric space group D3d3(P3m1) for their structure. The infrared and Raman spectra of La2O3 and Nd2O3 have been obtained and the absence of coincidences between the spectra unequivocally favours the centrosymmetric space group. The vibrational spectra have been analysed using the Wilson FG matrix method and force constants for metal-oxygen and oxygen-oxygen interactions derived, assuming a quadratic central force field.