You will find data and references to phases of nickel hydroxides
(which differ in composition) in Colin Greave's neutron paper:
J.Solid State Chem. 71 (1987) P. 418-425
Alan Hewat, ILL Grenoble, FRANCE <hewat@ill.fr> tel (33) 4.76.20.72.13
ftp://ftp.ill.fr/pub/dif fax (33) 4.76.48.39.06 http://www.ill.fr/dif/