Single crystal neutron diffraction study of sodium cyanide

Abstract

The neutron diffraction pattern of a single crystal of cubic NaCN has been measured at 295°K. These data and earlier results for KCN at 180 and 295°K have been analyzed in terms of a model which expands the angular distribution of CN− orientations in symmetry-adapted spherical harmonics. From this analysis, the distributions of CN− in these crystals have been derived, and these indicate a monotonic trend in the series KCN (295°K) thru KCN (180°K) to NaCN (295°K) involving a shift in preferential orientation from the [111] toward the [100] directions in the crystal. Unusually large translational Debye-Waller factors have also been derived for NaCN and KCN from the fitting procedure, in agreement with earlier results and analysis on KCN. In addition, an average C≡N bond distance of 1.18 Å is obtained.