Cu/Ag EAM异质外延扩散势的从头算优化
Cu/Ag EAM Potential Optimized for Heteroepitaxial Diffusion from ab initio Data
摘要：
通过对从头计算数据的拟合，优化了Cu/Ag（111）的二元嵌入原子方法（EAM）势。拟合数据库包括Ag（111）上Cu单体和二聚体的DFT计算，特别是它们的相对能量、吸附原子高度和二聚体分离。我们从Mishin Cu-Ag EAM势开始，首先修改Cu-Ag对势以匹配FCC/HCP位点能量差，然后包括整个数据库的Cu-Cu对势优化。优化后的EAM势正确地再现了DFT单体和二聚体的相对能量和几何构型。在三聚体计算中，虽然预测了不同的基态，但势能产生FCC和HCP三聚体之间的DFT相对能量。我们使用优化的电位来计算铜单体，二聚体和三聚体的扩散势垒。预测的单体势垒与DFT相同，而单体和二聚体的实验势垒都低于这里预测的。我们将与实验的差异归因于DFT对表面吸附能的高估，并提出了一个简单的修正。我们的研究结果表明，优化的Cu-Ag EAM可以应用于Ag（111）上较大的Cu岛的研究。
英文摘要：
A binary embedded-atom method (EAM) potential is optimized for Cu on Ag(111) by fitting to ab initio data. The fitting database consists of DFT calculations of Cu monomers and dimers on Ag(111), specifically their relative energies, adatom heights, and dimer separations. We start from the Mishin Cu-Ag EAM potential and first modify the Cu-Ag pair potential to match the FCC/HCP site energy difference then include Cu-Cu pair potential optimization for the entire database. The optimized EAM potential reproduce DFT monomer and dimer relative energies and geometries correctly. In trimer calculations, the potential produces the DFT relative energy between FCC and HCP trimers, though a different ground state is predicted. We use the optimized potential to calculate diffusion barriers for Cu monomers, dimers, and trimers. The predicted monomer barrier is the same as DFT, while experimental barriers for monomers and dimers are both lower than predicted here. We attribute the difference with experiment to the overestimation of surface adsorption energies by DFT and a simple correction is presented. Our results show that the optimized Cu-Ag EAM can be applied in the study of larger Cu islands on Ag(111).
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