NUCLEAR-MAGNETIC-RESONANCE STUDY OF THE ELECTRONIC-STRUCTURE AND HYDROGEN DIFFUSION IN THE RANDOM BCC VYTA1-Y-H(D) SYSTEM

Nuclear magnetic resonance measurements of the H-1, D-2 and V-51 spin- lattice relaxation rates and the V-51 Knight shifts in the random b.c. c. VyTa1-yHx(D-x) system (0.25 less than or equal to y less than or eq ual to 0.85, 0.07 less than or equal to x less than or equal to 0.4) h ave been performed in the temperature range 11-430 K. The relaxation d ata are analyzed to obtain the parameters of H(D) diffusion which is g overned by a distribution of activation energies. In different y range s the dependencies of the average activation energy (E) over bar(a) on hydrogen concentration are found to differ qualitatively. Comparison of the parameters of H and D diffusion in the samples of nearly the sa me composition shows that there is a distinct isotope effect: (E) over bar(a)(D)>($) over bar(a)(H). The behaviour of the density of electro n states at the Fermi level as a function of y and x is discussed on t he basis of the measured values of the V-51 Knight shifts and the elec tronic (Korringa) contributions to the spin-lattice relaxation rate. ( C) 1998 Elsevier Science S.A. All rights reserved.