Abstract We use a Tight-Binding Ising Model (TBIM) with effective pair interactions depending on concentration able to reproduce the bulk phase diagram of Pt-Ag system and in particular its strong asymmetry as a function of composition. This system presents both an L11 ordered structure around equiconcentration and a wide miscibility gap on the Pt-rich side. Using Monte Carlo simulations in canonical and semi-grand canonical ensembles, we succeed in reproducing qualitatively the bulk phase diagram and we study the equilibrium configurations of the (111) and (100) surfaces, and truncated octahedron clusters. The infinite surfaces reproduce sensibly the bulk phase diagram except that they present a strong silver surface segregation limited to the top surface layer. The clusters behave differently due to the reduction of the miscibility gap when decreasing the cluster size and present two typical ordered phases related to the L11 phase: one characterized by pure concentric atomic layers starting from silver surface layer which extends up to the center of the cluster, and the other one at higher silver concentration where the L11 phase is perfectly oriented along one (111) direction of the cluster. The later one has already been reported by recent experiments [1].

中文翻译：

---

Pt-Ag 纳米合金中批量排序和表面偏析之间相互作用的紧密结合 Ising 建模。

摘要 我们使用具有取决于浓度的有效配对相互作用的紧密结合伊辛模型 (TBIM)，能够再现 Pt-Ag 系统的体相图，特别是其作为组成函数的强不对称性。该系统呈现出围绕等浓度的 L11 有序结构和富铂侧的宽混溶间隙。在正则和半正则集合中使用蒙特卡罗模拟，我们成功地定性地再现了体相图，并研究了 (111) 和 (100) 表面的平衡配置，以及截断的八面体簇。无限表面明显地再现了体相图，只是它们呈现出仅限于顶面层的强银表面偏析。由于减小团簇尺寸时混溶间隙的减小，团簇的行为有所不同，并呈现出与 L11 相相关的两种典型有序相：一种以纯同心原子层为特征，从银表面层开始一直延伸到团簇的中心，而另一个银浓度较高，其中 L11 相沿簇的一个 (111) 方向完美取向。最近的实验已经报道了后者[1]。