DETERMINATION OF VANADIUM OXYGEN BOND DISTANCES AND BOND ORDERS BY RAMAN-SPECTROSCOPY

An empirical correlation is developed for relating Raman stretching frequencies of vanadium-oxygen (V-O) bonds to their bond lengths in vanadium oxide reference compounds. A least-squares exponential fit of crystallographically determined V-O bond lengths to V-O Raman stretching frequencies is presented along with a relation between V-O bond strengths (in valence units) and Raman stretching frequencies. These empirical correlations lead to a systematic method for determining the coordination and bond lengths of vanadates. This method is illustrated for vanadates of known structure (vanadium n-propoxide, BiVO4, alpha-Zn3(VO4)2, and Pb2(VO4)3Cl) and unknown structure (AlVO4 and two-dimensional surface phase in V2O5/Al2O3). The method is expected to be generally applicable to all vanadates where medium-range order is absent.