Quantitative measure of local solidity/liquidity in metallic glasses

Metallic glasses are viscoelastic materials that contain a wide spectrum of local configurations that range from more “solid-like” to more “liquid-like” varieties. To quantitatively characterize the local solidity (or liquidity) in metallic glasses, here we present a robust method and a universal materials parameter. The new parameter, solidity (liquidity) index, is based on the evaluation of bond orientational anisotropy. The usefulness of the proposed index in assessing the varying degrees of solidity (or liquidity) is demonstrated in metallic glass models produced via molecular dynamics simulations. The spectrum of local solidity is also analyzed in terms of its dependence on local structural features, particularly on the basis of different types of Voronoi polyhedra and atomic volume.