The e/a values of ideal metallic glasses in relation to cluster formulae

Abstract The electrons per atom ratio e / a is an important factor in discussing the stabilization mechanism of metallic glasses. However, the e / a assignment is complicated by hybridization effects, particular in transition metal systems. We have previously proposed the “cluster-plus-glue-atom” model for metallic glasses and the relevant cluster formula [cluster](glue atom) x , x ∼ 1 or 3. In the present paper, this model is combined with Haussler’s global-resonance model into a so-called cluster-resonance model. This model allows the calculation of the Fermi vector and hence the effective e / a of an ideal metallic glass. By assuming an ideal dense packing of the clusters, the atomic density can be obtained and e / a becomes associated with the number of atoms in the unit cluster formula Z . Experiments are carried out to verify these correlations. Alloys like Cu 8 Zr 5 Al, Ni 4 Zr 9 Al 2 and [Ni 7 Nb 5 Zr]Ni 3 , possessing locally the highest glass-forming abilities, are interpreted by cluster formulae, with their Z s being determined by their e / a values. Such verifications not only validate the proposed e / a calculation schemes and the models behind them, but also support the ideal metallic glass feature of bulk metallic glasses with high glass-forming abilities.