Invariant topological feature of atomic packing in a model metallic glass

Abstract

Establishing a quantitative structure-property relationship is essential for the development and design of new materials. However, this approach faces significant challenges in amorphous materials, where even a quantitative description of atomic structure is nearly impossible. In this study, we examined the packing characteristics of atoms based on their contributions to excess low-frequency vibrational modes in a model metallic glass. Our investigation spans more than eight orders of magnitude in effective cooling rates, ensuring the exploration of a broader range of thermal history states and their associated properties. We found that atoms with smaller contributions tend to cluster spatially, while those with larger contributions form branched, quasi-two-dimensional structures with fractal characteristics. As a result, the critical fraction of atoms required to form a percolated network is significantly lower for high-contribution atoms than for low-contribution ones. In both types of networks, the correlation between connectivity and contribution follows an exponential relationship, with higher sensitivity in networks composed of large-contribution atoms. As the system's energy decreases, the intensity of the low-frequency excess peak diminishes, yet the critical fraction of atoms remains constant, irrespective of whether the networks are composed of high- or low-contribution atoms. This reveals a hidden topological invariance in the atomic packing features of metallic glasses.