Stability of the Zr-based amorphous alloys evaluated from the electronic structure of their basic clusters

The electronic structure stability of the Zr-based amorphous alloys is investigated through clusters derived from the primary devitrification phases such as fcc-Zr2Ni and bct-Zr2Cu in the Zr-based amorphous alloy. Two clusters are selected, Zr9Ni4 and Zr10Cu5 respectively for Zr–Ni-based and Zr–Cu-based alloys. The stability of these clusters is obtained by the discrete variational method based on first-principles calculation. Two important parameters associated with the stability of the amorphous alloys are introduced, the bond order that measures the bonding strength between different atoms, and the density of states at the Fermi level. Element Al changes the bond order of Zr, Ni, and Cu in the clusters and reduces the density of states at the Fermi level. The improvement of stability explains the superior stability of the Zr–Al–Ni and Zr–Al–Cu amorphous alloys with respect to the binary Zr–Cu and Zr–Ni amorphous alloys.