发表机构
University of Brasília; College of Technology, University of Brasília（巴西利亚大学; 巴西利亚大学技术学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究结合穷尽枚举与密度泛函理论研究有序Au-Ag-Cu单原子层合金，发现原子排列控制混合能，提出等摩尔结构Noblene，其具动态稳定性等特性，或可从Goldene出发合成。
AI 中文摘要
二维金属因通过化学插层剥离得到单原子厚金片Goldene而成为实验室现实，这提出了在同一密排晶格上合金化能实现何种效果的问题。本文将衍生超结构的穷尽枚举与密度泛函理论相结合，绘制有序Au-Ag-Cu单原子层合金的图谱，对每个晶胞内最多4个原子的所有对称性不等价排列进行弛豫，并通过拟合模型选择更大的晶胞以扩展研究范围。研究发现，原子的排列而非其比例控制混合能，因为同一成分的不同排列之间的能量差是相邻成分之间差别的数倍，某一成分的三个原子的两种排列之间每原子能量差超过50 meV，且在两种成分下排列决定了能量的符号。能量学由结合的Au-Cu接触与不结合的Ag-Cu接触之间的竞争决定，在相同协议下计算的体焓表明，这种化学作用在二维中并非均匀缩放，因为Au-Cu在单原子层中的有序性强于晶体中，而另外两种则减弱。一个由弹性尺寸失配项补充的对模型能以每原子几meV的精度重现计算能量，并返回一个凸包没有平衡三元成分能达到的成分图谱。一种等摩尔排列（命名为Noblene）是唯一每个原子仅被不同种类原子包围的结构，它具有动态稳定性和金属性，泊松比高于0.5，高于三种纯单原子层的泊松比。由于Noblene位于Goldene已实现的晶格上，制备Goldene的路线是其合成的合理起点。
英文摘要
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 the arrangement of the atoms, and not their proportion, controls the mixing energy, since the spread among the orderings of a single composition is several times the step between neighboring compositions, one composition spans more than 50~meV/atom between two arrangements of the same three atoms, and at two compositions the arrangement 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 this chemistry is not uniformly rescaled in two dimensions, since Au-Cu orders more strongly in the monolayer than in the crystal while the other two weaken. A pair model completed by an elastic size-mismatch term reproduces the computed energies to a few meV/atom and returns a composition landscape whose convex hull no balanced ternary composition reaches. 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 a Poisson's ratio above one half, higher than that of any of the three 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.
Comments18 pages, 6 figures, 1 table
