Turing Pattern and Chemical Medium-Range Order of Metallic glasses

TL;DR

This paper introduces a novel method using persistent homology from molecular dynamics simulations to analyze chemical medium-range order in metallic glasses, revealing their Turing pattern-like topology and dependence on interatomic potentials.

Contribution

It presents a new topological approach to characterize chemical ordering in metallic glasses, linking medium-range order to interatomic potential depths and Turing pattern formation.

Findings

Chemical medium-range order can be evaluated using persistent homology.

Metallic glasses exhibit a Turing pattern topology regulated by elemental interactions.

Chemical ordering correlates with the depth of interatomic potential wells.

Abstract

The formation of bulk metallic glass requires the constituent elements to have a negative heat of mixing but has no restrictions on its magnitude. An understanding of this issue is lacking due to the absence of a valid method for describing chemical ordering of metallic glasses. For example, the radial distribution function is ineffective in identifying the elemental preferences of packed atoms. Here, we show that using molecular-dynamics simulation, the chemical medium-range ordering of liquid alloys can be evaluated from persistent homology. This inherently arising chemical medium-range order in metallic glasses is exclusively regulated by the activation and inhibition of the constituent components, making the topology of metallic glasses a Turing pattern. The connecting schemes of atoms of the same species form three distinct regions, reflecting different correlations at the short and medium length scales, while the difference in the schemes corresponds to chemical ordering. By changing the elemental types, it is demonstrated that the chemical medium-range order strongly depends on the relative depth of the interatomic-potential wells. The study separates metallic glasses from crystals under the condition of negative heat of mixing by emphasizing their fundamental difference in interatomic potentials.