Thermal desorption spectra of hydrogen from the bulk: ZrV₂H_x

Thermal desorption of hydrogen from the bulk of the system ZrV₂H_x, 0.3 ≤ x ≤ 4.27, shows spectra which develop from a single peak, for x < 1, to a spectrum that consists of 3 peaks and a shoulder for x ≤ 4.27. A model is proposed to explain the origin of these peaks and relates them to a consecutive desorption of the hydrogens from the different interstitial sites, in agreement with neutron diffraction data on the sites' occupancy. However, neutron diffraction indicates that up to x ≈ 2.5 the hydrogens occupy the tetrahedral sites formed by 2 Zr and 2 V, nevertheless our results show that there is a large difference in the bonding energy of these sites for hydrogens with x < 1 and hydrogens with 1 < x < 2.5.