2D rotation–translation coupling with planar molecules

Abstract

A structure-factor calculation for two-dimensional rotation-translation coupling with planar molecules is presented. The starting point is a continuous description of the scattering-length-density distribution for a planar molecule that rotates around its symmetry axis. For the example of a molecule with threefold symmetry at a site with fourfold symmetry, the successive correction terms to the conventional rotational form factor are evaluated. This approach yields results equivalent to the split-molecule model. This is shown by an example of a structure refinement on Ni(ND3)6Br2 single-crystal data.