Nuclear magnetic resonance measurements of 'H, 'D and "V spin-lattice relaxation rates T;' in TaV2H.JDI) (0.22 C x C 1.54) have been performed over the temperature range 10-440 K. For all the studied samples the double-peak temperature dependence of T;' is observed. The high-temperature relaxation rate maximum is associated with H(D) diffusion, and the low-temperature one is attributed to localised motion of H(D) atoms. The experimental results are analysed to obtain the parameters of the two types of motion as functions of temperature and H(D) content. At 300 K the diffusion rate is found to increase with increasing H(D) concentration. The characteristic period of the localised motion, bL, exhibits unusual temperature dependence, tLexp(-T/T,,) with To = 50 K.

Measurements of the temperature dependence of the 1H, 2D and 51V spin lattice relaxation rates T1-1 in TaV2Hx (Dx) show a second low-temperature T1-1 maximum in addition to the usual maximum associated with H(D) diffusion. This feature can be attributed to low-frequency local motion of H(D) atoms. Strong effects of hydrogen isotope substitution are observed at low temperatures.

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Nuclear magnetic resonance measurements of 1H and 2D spin-lattice relaxation times in HfV2Hx(Dx)(0.53.5 there is a distinct isotope effect in Ea for the disordered phase: EaD

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