Defects identifier based on coarse grained equivalent stiffness gradient in 2D metallic glasses

Intensive parameters have focused on identification of defects in metallic glasses (MGs), a long-standing stymy due to the lack of long-range order. Rather than diagonalizing full Hessian matrix, here we introduce Coarse Grained Equivalent Stiffness (CGES), which is based on the determinant of local Hessian matrix (LHM), to describe heterogeneities of MGs. Atomic nonaffine displacements (ANDs) are determined by external loadings and internal heterogeneities, so that certain shapes of CGES gradient fields lead to shear-like or dilation-like ANDs, revealing the physical mechanism of local shear, shear-induced dilatancy and dilation. Further molecular simulations indicate that approximate spatial distributions of atoms, which would experience shear or volumetric deformation before yielding, can be estimated by initial CGES gradient fields. These results provide insights into the structural origin of anisotropic defects in MGs.

Automated summary

This study introduces the Coarse Grained Equivalent Stiffness (CGES) method to characterize the heterogeneities of metallic glasses (MGs) based on the determinant of local Hessian matrix (LHM), revealing the physical mechanism of local shear, shear-induced dilatancy, and dilation. Molecular simulations also predict the spatial distribution of atoms experiencing shear or volumetric deformation before yielding.