Optical Properties and Chemical Ordering of Ag-Pt Nanoalloys: A Computational Study

A series of core-shell and layered ordered-phase AgPt bimetallic clusters have been studied with Ag:Pt = 3:1 and 6:1 compositions and sizes from 116 to 201 atoms. Chemical order has been established by using a recent method (TOP) that assigns energy according to topological degrees of freedom. Lowest energy structures determined by density functional calculations are then studied by time-dependent density functional theory to calculate optical properties. The present study shows that for AgPt nanoparticles with core-shell structure the optical properties are sensitive to both Pt concentration and cluster size. Spectral trends related to modifying chemical order have also been identified.