Crystal structure and dynamics of Mg(ND3)6Cl2

Abstract

The crystal structure and dynamics of Mg(ND₃)₆Cl₂ have been investigated by powder neutron diffraction and molecular dynamics. The powder diffraction data can be well described by 4 partly occupied deuterium sites in a square arrangement around the N atoms, which is seemingly inconsistent with the 3-fold symmetry of the ND₃ molecule. Molecular dynamics show highly correlated rotational and translational motion of the ND₃ molecules which explains the apparent 4-fold symmetry of the deuterium arrangement. A more disordered structure model based on the molecular dynamics results gives a better fit to the experimental data and is in agreement with the 3-fold symmetry of ND₃.