The crystal structure of Ni5(AsO4)2(OH)4 and its comparison to other M5(XO4)2(OH)4 compounds
published: Feb 22, 1996
manuscript accepted: Sep 14, 1995
manuscript received: May 5, 1995
ArtNo. ESP147050801009, Price: 29.00 €
Abstract The structure of a new nickel arsenate hydroxide, Ni5(AsO4)2(OH)4, has been determined by single-crystal X-ray diffraction (R(F) = 0.045 for 1469 observed reflections with F0 > 4σ(F0)). This new compound is isostructural with the mineral reppiaite, Mn5(VO4)2(OH)4. Its unit-cell has C2/m symmetry with the parameters a = 9.291(2), b = 9.008(2), c = 5.149(1) Å, ß = 98.70(3)° and Z = 2. The Ni5(AsO4)2(OH)4 structure is based on a regular cubic close-packing of oxygen atoms and is built of alternating octahedral (NiO6) and tetrahedral (AsO4) layers, stacked in a four-layer repeat along the a direction. Bond valence calculations have been used to locate the OH groups in the structure. The structural similarities and differences with other M5(XO4)2(OH)4 compounds are described.