Neutron diffraction study of the orientational disorder in Ni(ND3)6Br2

The ND3 group is in the high temperature phase of the title compound dynamically disordered. Fourier maps derived from the analysis of neutron single crystal Bragg data with phases based on a split atom and a Frenkel model show uniquely that each D3 group has four density maxima occupying the corners of a square. Neither one nor three dimensional models of purely rotational disorder can describe the observations adequately.