DIRECT MEASUREMENT OF THE HYDROGEN-HYDROGEN CORRELATIONS IN HYDROGENATED AMORPHOUS NI56DY44 BY NEUTRON-DIFFRACTION

From an isotopic mixture of dysprosium with zero neutron scattering le ngth and an isotopic mixture of nickel with zero neutron scattering le ngth ribbons of the amorphous alloy Ni56Dy44 were produced by melt-spi nning and loaded with 59 at% deuterium. A neutron diffraction experime nt yielded directly the deuterium-deuterium partial structure factor S -DD and the partial pair correlation function G(DD). The incorporation of the D-atoms into the amorphous matrix shows an ordering up to five coordination shells at least. The main peak of G(DD) is split up into a contribution at 2.36 Angstrom with 5.4 nearest neighbours and a con tribution at 2.76 Angstrom with 4 neighbours. The D-atoms are located preferentially in Dy-4-tetrahedra, where the occupation of two neighbo uring face-sharing tetrahedra is avoided.