Single-Crystal X-Ray Diffraction Study of Na[OCN] at 170 K and its Vibrational Spectra

Abstract

The unit cell of Na[OCN] has been determined on single crystals at 170 K to have rhombohedral symmetry with the lattice parameters a = 356.79(10) and c = 1512.3(5) pm (hexagonal setting). According to the only model for which a converging refinement could be achieved, Na[OCN] crystallizes isopointal to β -NaN3 in the space group R¯3m (no. 166, Z = 3) with a statistically disordered [OCN]− anion. The positional coordinates and displacement parameters could not be separated for the O and N end atoms of the triatomic anion. The vibrational spectra show the frequencies typical for an [OCN]− moiety with Fermi resonance between the 2δ and the νsym vibrations for which the undisturbed frequencies were calculated.