Local structure investigation of β-Ni(OH)2 under pressure using combined Raman and Ni K-edge extended x-ray absorption fine structure studies

C. Marini, B. Joseph, S. Caramazza, F. Capitani, M. Bendele, Innokenty Kantor, P. Lotti, O. Mathon, S. Pascarelli, P. Postorino

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We present a combined high pressure Ni K-edge x-ray absorption and Raman spectroscopic investigation of β-Ni(OH)2. Extended x-ray absorption fine structure analysis reveals a progressive shrinking of the Ni-O and Ni-Ni bond distances with pressure. As pressure is increased, Raman data show a continuous hardening of the phonon modes associated with the vibration of Ni-O sublattice, whereas a systematic frequency softening is displayed by the hydroxyl (O-H) symmetric stretching mode. This contrasting behavior implies a gradual development of a lattice instability with pressure in nickel hydroxide. Under pressure hydrogen bonds become increasingly unstable mainly due to the displacement of H atoms around the Ni-O axis inducing a local-lattice instability may explain the structural, Raman and x-ray absorption results.
Original languageEnglish
JournalHigh Pressure Research
Issue number1
Pages (from-to)1-10
Number of pages10
Publication statusPublished - 2017
Externally publishedYes


  • High pressure

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