The Raman and infrared spectra of CaNb2O6 are assigned by normal coordinate analysis according to Shimanouchi’s method. The Raman spectroscopy results enabled us to refine the force field, which was then checked by the infrared spectroscopy results. The obtained force constants show that there are three different types of Nb–O bonds in the columbite structure and that the Ca–O bonds are of electrostatic nature. The potential energy distribution calculation gives us a precise assignment for all the observed frequencies.
Normal coordinate analysis of the MNb2O6 series of columbite structure (M=Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn, Cd) was carried out and the results obtained permitted the assignment of all the observed vibrational bands of the columbite series. It is also shown that the force fields of the columbite series are very similar when cations are changed. The variations are interpreted as due to the mass, the electronegativity, and the positions of the cations in the periodic table. The order of the bonds is also given.
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