THERMODYNAMIC PROPERTIES OF HYDROGEN IN QUASI-2-DIMENSIONAL VANADIUM LATTICES

The solubility and thermodynamics of hydrogen in quasi-two-dimensional vanadium lattices have been investigated. The quasi-two-dimensional character of the vanadium lattices were obtained by growing alternating layers of molybdenum and vanadium in Mo/V superlattice structures. The hydrogen solubility was found to be higher in the thin V layers than in bulk vanadium. The enthalpy change, <Delta(H)over bar (H)>, reached a value of -0.42 eV per H atom after a steep increase from the infinite-dilution limit (-0.28 eV per H atom). The entropy change, <Delta(S)over bar (H)>, is found to decrease for the thin V layers compared to bulk vanadium for hydrogen concentrations up to H/V = 0.2. Above 0.2, <Delta(S)over bar (H)> reached the bulk values.