The influence of structural disorder on the hydrogen absorption in amorphous and crystalline Pd-Si alloys

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Abstract
The absorption of hydrogen in several amorphous Pd-Si alloys as well as in crystallised Pd80Si20 is studied experimentally for hydrogen pressures up to 50 bar and temperatures between 333 and 493K. The absorption of hydrogen is detected in situ with a combined dilatometric/resistometric apparatus and with a microbalance. From a comparison of these measurements useful relations between lattice expansion, resistance increase and hydrogen content are determined. The pressure-composition isotherms of the structurally disordered host metals are described theoretically by a gaussian distribution of site energies, in combination with a nonlocal effective H-H interaction that arises from elastic and electronic changes in the host metal. From the concentration dependence of the interaction energy, it is deduced that the Fermi level in the glass-forming Pd-Si alloys is located at a minimum of the electronic density of states.