We performed a theoretical study of the chemical ordering and surface segregation of Pt–Ag nanoalloys in the range of size from 976 to 9879 atoms (3.12 to 6.76nm). We used an original many-body potential able to stabilize the L1₁ ordered phase at equiconcentration leading to a strong silver surface segregation. Based on a recent experimental study where nanoparticles up to 2.5nm have been characterized by high transmission electron microscopy with the L1₁ ordered phase in the core and a silver surface shell, we predict in our model via Monte Carlo simulations that the lower energy configuration is more complicated with a three-shell alternance of Ag/Pt/Ag from the surface surrounding the L1₁ ordered phase in the core. The stress analysis demonstrates that this structure softens the local stress distribution inside the nanoparticle which contributes to reduce the internal energy.

我们对 976 至 9879 个原子（3.12 至 6.76nm）尺寸范围内的 Pt-Ag 纳米合金的化学排序和表面偏析进行了理论研究。我们使用了一个原始的多体势能，能够在等浓度下稳定 L1 ₁有序相，从而导致强烈的银表面偏析。基于最近的一项实验研究，其中高达 2.5nm 的纳米粒子已通过高透射电子显微镜进行表征，其中核中的 L1 ₁有序相和银表面壳，我们通过蒙特卡罗模拟在我们的模型中预测，较低的能量配置是更复杂的是从 L1 ₁周围的表面的 Ag/Pt/Ag 的三壳交替核心中的有序相。应力分析表明，这种结构软化了纳米粒子内部的局部应力分布，有助于降低内能。