EVIDENCE FOR PARTIAL (SUBLATTICE) AMORPHIZATION IN CO(OH)(2)

Infrared absorption and Raman spectroscopy under pressure document tha t the O-H bands of crystalline Co(OH)(2) become disordered when the sa mple is compressed to 11.2 (+/-0.3) GPa at room temperature. The disor der is reversible on decompression, but involves only the H sublattice : x-ray diffraction shows that the Co-O sublattice of Co(OH)(2) retain s long-range order between 0 and 30 GPa. The results document a novel form of pressure-induced disordering, sublattice amorphization, and im ply that amorphization transitions can be staged, with the crystal --> glass transition being achieved through the successive disordering of sublattices.