Neutron Diffraction Study of Solid Deuteroammonia

摘要

The crystal structure of the stable cubic modification of solid deuteroammonia has been determined by neutron diffraction. The space group isP213mdash;T4, and at mdash;196deg;C the positions of the atoms are 4N at (a) withu=0.2127plusmn;0.0021 and 12D at (b) withx=0.3740plusmn;0.0019,y=0.2632plusmn;0.0037, andz=0.1094plusmn;0.0016. Each nitrogen atom is hydrogen bonded to the six nearest neighbor nitrogen atoms. There is one deuterium atom per site, in contrast to the ``halfhyphen;hydrogen'' structure of ice. The Nmdash;D bond length of 1.005plusmn;0.023 A is indistinguishable from that of the free molecule, while the Dmdash;Nmdash;D bond angle of 110.4deg;plusmn;2.0deg; is appreciably larger than the free molecule value.