High-pressure behavior of β-Ni (OH)2 -: A Raman scattering study

The existence of very short non-bonded H-H distances in beta -Ni(OH)(2) at ambient conditions, predisposes this compound towards a structural change at very low pressures. To investigate this, we have now carried out a high-pressure Raman scattering investigation on beta -Ni(OH)(2) up to 25 GPa. Our results show a monotonic stiffening of all the lattice modes and a small softening of hydroxyl symmetric stretch mode under pressure. Absence of any signature of a phase transformation up to 25 GPa and a reversible intrinsic broadening of the OH mode suggest that, even at the ambient conditions, beta -Ni(OH)(2) may be in the non-ideal CdI2, structure in which H-lattice is disordered. (C) 2001 Elsevier Science B.V. All rights reserved.