Existence of fractal packing in metallic glasses: Molecular dynamics simulations ofCu46Zr54

The recently advocated power-law scaling for fractal packing in amorphous metals is examined in a metallic glass under hydrostatic pressure. We show that the scaling relation ${v}_{a}\ensuremath{\sim}{q}_{1}^{\ensuremath{-}\ensuremath{\zeta}}$ between the sample molar volume ${v}_{a}$ and the first peak position ${q}_{1}$ in the scattering function exhibits a varying exponent \ensuremath{\zeta} from 2.77 to 3.72 in different stages of compression, rather than a constant as the universal fractal dimensionality. Fractal packing of short- and medium-range icosahedral clusters is found to exist but undetectable with high angle scattering. Therefore, the substructure of the metallic glass does not contribute to the power-law exponent. Moreover, we show that the space filling contributed from different alloy components with varying atomic sizes is overlooked in the scaling relation that gives rise to the so-called fractal dimension. The amorphous packing of metallic glasses is actually compact with dimension 3.