Vibrational density of states in amorphous Ni1−xBx alloys and c-Ni2B

Abstract

Inelastic neutron scattering measurements are reported on the amorphous (a) transition-metal–metalloid alloys of a-${\mathrm{Ni}}_{82}$ ${\mathrm{B}}_{18}$, a-${\mathrm{Ni}}_{67}$ ${\mathrm{B}}_{33}$, and the crystalline (c) compound, c-${\mathrm{Ni}}_2$B. The spectra provide information about changes in the vibrational density of states with composition and upon crystallization. The results of the crystalline-to-amorphous comparison for the 67 at. % Ni samples, show dramatic changes in the vibrational spectra, including an increase in the number of states, both at low and high energies, in the amorphous sample. The differences in the high-energy states are attributed to a change in short-range order between the amorphous and crystalline compositions. The similarities between the 67 at. % Ni and 82 at. %Ni samples are consistent with a similar short-range order in the two alloys, as well as comparable transition-metal–transition-metal and transition-metal–metalloid interactions. No evidence for any appreciable, direct metalloid-metalloid bonding in the high-metalloid-content samples has been found.