Deuteron dynamics and its isotope effect in β-Ti 1− yV yDx as studied by 2H NMR

Abstract

Deuteron dynamics and its isotope effect in disordered metal deuterides, β-Ti 1− y V y D x ( x∼1 and 0.2≤ y≤0.8) were studied by 2H NMR. Temperature dependence of 2H spin-lattice relaxation times ( T 1) was measured over the temperature range 125–400 K. All the deuterides exhibited a minimum in ln( T 1) vs. 1/T curves, which originated from the fluctuation of the quadrupole interaction due to the deuteron diffusion. The quadrupole coupling constant (QCC) for the deuteron and the activation parameters were determined from the T 1 data analysis with Bloembergen-Purcell-Pound (BPP) theory taking account of the distribution of the correlation time. The QCC values, which were within the range of 21∼36 kHz, made it possible to assign the deuteron site in the alloys to the tetrahedral site. The remarkable isotope effect was found in the activation energy E a for the hydrides and the deuterides. The difference in the E a between the deuterides and the hydrides, E a D− E a H, was interpreted qualitatively by the atomic mass effect and the difference in the manner of site occupation between the hydrides and the deuterides.