The crystal structure of ammonium oxide

At low temperatures ammonia forms two stable hydrates NHs.H~O and 2NHs.H~O , ammonium hydroxide and ammonium oxide respectively. The hydroxide is hexagonal with a = 11-21=1=0.05/~ and c = 4.530.02/~ at --95:t= 10 C. The oxide is orthorhombic (space group Pbnm) with a = b = 8.410.03 /~ and c = 5-330.02 /~ at --9510 C. The structure of ammonium oxide contains planar chains of alternating ammonia and water molecules bonded by hydrogen bonds of the OH... N and N-H. O type. The chains are cross linked into a three-dimensional lattice by hydrogen bonds of the latter type. The open spaces in the lattice contain the remaining ammonia molecules, each having a single hydrogen bond to the molecular lattice.