Hydrogen motion and site occupation in Ti2CoHx(Dx): NMR and neutron scattering studies

✍ Scribed by A.V. Skripov; A.L. Buzlukov; A.V. Soloninin; V.I. Voronin; I.F. Berger; T.J. Udovic; Q. Huang; J.J. Rush

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 857 KB
• Volume: 392
• Category: Article
• ISSN: 0921-4526
• DOI: 10.1016/j.physb.2006.12.002

✦ Synopsis

Nuclear magnetic resonance measurements of the 1 H and 2 D spin-lattice relaxation rates R 1 for Ti 2 Ni-type compounds Ti 2 CoH 0.5 , Ti 2 CoH 0.9 and Ti 2 CoD 1.0 have been combined with inelastic neutron scattering (INS) measurements of the H(D) vibrational spectra and neutron diffraction measurements for the same samples. The R 1 results for Ti 2 CoH 0.9 and Ti 2 CoD 1.0 give evidence for the existence of a fast H(D) motion with the characteristic jump rate of about 3 Â 10 8 s À1 at room temperature, whereas for Ti 2 CoH 0.5 such a fast motional process is absent. The results of the INS and neutron diffraction measurements suggest that the appearance of the fast hydrogen jump process in Ti 2 CoH x (D x ) with xE1 is related to the occupation of an additional type of interstitial sites by hydrogen atoms. While in Ti 2 CoH 0.5 , hydrogen atoms are found to occupy only the octahedral sites with Ti 6 coordination, a partial occupation of the tetrahedral Ti 3 Co and Ti 2 Co 2 sites by H(D) atoms (in addition to the nearly completely filled sublattice of the octahedral sites) has been revealed for Ti 2 CoH 0.9 and Ti 2 CoD 1.0 . Possible paths of hydrogen jump motion in Ti 2 CoH x (D x ) are discussed on the basis of the distances between the sites partially occupied by H(D) atoms.