Positron Annihilation in Pd-Ag-H and Pd-Au-H Systems

Positron annihilation method was used to study hydrogenated Pd$\text{}_{1-y}$Ag$\text{}_{y}$, and Pd$\text{}_{1-y}$Ag$\text{}_{y}$ alloys in α-phase. In both systems, insensitivity of the low-lying core states to the presence of hydrogen in the alloy was found. Rigid band mode1 appeared to be a useless description of the changes in the band occupation after hydrogen absorption. The results seem to indicate that the "capacity" of the low-lying H-Pd bonding states remains constant when the Ag or Au atoms are added to PdH$\text{}_{≈0.6}$, which can explain the existence of the limit to the summed up hydrogen and Ag(Au) concentration.Zatwie