Electrostatic properties of ammonium fluoride and deuterated ice-Ih

New single crystal X-ray diffraction data have been collected at reduced temperature (120 K) and high resolution (sinθ/λ ≤ 1.34 A−1) for ammonium fluoride and for heavy ice-Ih, (D2O) in order to determine the detailed electron density distribution in these structures. The crystals are isostructural. Ammonium fluoride, NH4F, is hexagonal with space group P63mc, a = 4.4365(3), c = 7.1672(5) A, Z = 2. Ice-Ih, D2O, is hexagonal with space group P63/mmc, a = 4.4950(5), c = 7.3170(10) A, Z = 4. The X-ray data were collected with Nb-filtered MoKα radiation (λ = 0.7093 A). Refinements with Stewart's rigid pseudoatom model gave R(F2) = 0.016 for 292 reflections for NH4F and R(F2) = 0.023 for 296 reflections for ice-Ih. Hydrogen nuclear positions and mean-square displacements were taken from previous neutron diffraction studies. The structures each contain two crystallographically distinct H(D) atoms, namely, those with N-H or O-D directed along the c-axis and those that are directed tetrahedrally with respect to c...