Single-Crystal Structure and Electron Density Distribution of Ammonia at 160 K on the Basis of X-ray Diffraction Data

A single-crystal of ammonia, NH 3, was grown in a thin-walled capillary at 178 K, and high-resolution X-ray diffraction data were obtained for this compound at 160 K in order to obtain information about electron density distribution. Conventional and multipole refinements and deformation electron density maps indicated small but significant N−H bond bending inside the NH 3 tetrahedron that is in agreement with ab initio quantum-chemical calculations and the VSEPR model. Topological analysis of the experimental charge density distribution in the ammonia molecule has been performed, and the data are compared with high-level quantum-chemical calculations. Some features of the intermolecular hydrogen bonds in the crystal are discussed.