Experimental observation of hysteresis in a coherent metal-hydride phase transition.

We investigate the hysteresis obtained in the hydrogen absorption and desorption cycle for a single crystal [Formula: see text] superlattice. Below the critical temperature, a small but clear hysteresis is observed in the pressure-composition isotherms, while it is absent above. The experimental results thereby prove the relevance of macroscopic energy barriers for obtaining hysteresis in coherent structural transformations.

Concentration dependence of hydrogen diffusion in clamped vanadium (0 0 1) films.

The chemical diffusion coefficient of hydrogen in a 50 nm thin film of vanadium (0 0 1) is measured as a function of concentration and temperature, well above the known phase boundaries. Arrhenius analysis of the tracer diffusion constants reveal large changes in the activation energy with concentration: from 0.10 at 0.