Structure of glassy early-transition-metal-late-transition-metal hydrides

Hydrogen is used as a probe for obtaining structural information on metallic glasses. Results from experimental radial distribution functions of hydrided and unhydrided ${\mathrm{Zr}}_3$Rh and ${\mathrm{Zr}}_2$Pd glasses show a significant change in the nearest-neighbor distance of Zr atoms. The measured distance suggests that hydrogen occupies mainly tetrahedral sites defined by four Zr atoms under normal hydriding conditions (1 atm ${\mathrm{H}}_2$, ∼200°C). A statistical model for these sites based on current dense-random-packing models is in good agreement with the observed absorption capacity for hydrogen. We predict that H-H interaction should limit the upper value of hydrogen content in Zr-based glasses to 2.5 (H/metal atom).