P-O bond lengths-Raman frequencies correlation (Mn(PO_4)_m; M = M~I, M~(II))

摘要

A method for estimating metal-oxygen bond lengths in inorganic solids from their Raman spectra has been proposed by Hardcastle and Wachs [1] in 1991. Method is based on empirical correlation between crystallographically determined bond lengths and observed Raman stretching frequencies. Such direct relationship between these two experimental observables is expected from diatomic approximation where each distinct bond is vibrationally independent of the crystalline lattice. Vibrational interactions between neighboring chemical bonds are neglected, so the Raman spectrum is a superposition of the stretching frequencies from an assembly of diatomic oscillators. Each oscillator has a unique interatomic distance and exhibits a unique vibrational band. The method is expected to offer invaluable insight into the structures of species in chemical systems for which diffraction or other spectroscopic techniques provide incomplete structural information. This is expected to popularize Raman spectroscopy as a complementary technique in the structural studies.