  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.
