Year: 2026
Type: article
Abstract: Two-dimensional metals became a laboratory reality with the isolation of goldene, a gold sheet one atom thick released by chemical exfoliation, which raises the question of what alloying can achieve on the same close-packed lattice. Here we combine an exhaustive enumeration of derivative superstructures with density functional theory to map the ordered Au-Ag-Cu monolayer alloys, relaxing every symmetry-inequivalent arrangement up to four atoms per cell and extending the set with larger cells selected by a fitted model. We find that composition sets the scale of the mixing energy while the arrangement of the atoms adds a spread of 13 meV per atom within a fixed cell stoichiometry, a spread that at one stoichiometry exceeds 50 meV per atom between two arrangements of the same three atoms and at two stoichiometries decides the sign. The energetics is carried by a competition between Au-Cu contacts, which bind, and Ag-Cu contacts, which do not, and bulk enthalpies computed under the same protocol show that all three unlike-pair interactions strengthen per bond in the monolayer, with Au-Cu the outlier at more than twice its bulk value. A pair model completed by an elastic size-mismatch term reproduces the computed energies with a mean absolute error of 5.5 meV per atom and returns a composition landscape in which no balanced ternary composition is resolved as reaching the convex hull. One equimolar ordering, which we name noblene, is the only structure in which every atom is surrounded exclusively by unlike species, and it is dynamically stable and metallic, and carries the highest Poisson's ratio of the four, 0.507 against 0.448 for the highest of the pure monolayers. Since noblene sits on the lattice that goldene already realizes, the route that produced goldene is a plausible starting point for its synthesis.
Source: Materials Horizons
DOI: 10.1039/d6mh01971d
Author: Marcelo Lopes Pereira Junior
Institution: Universidade de Brasília
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7223368281