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DFT-Based Approach Enables Deliberate Tuning of Alloy Nanostructure Plasmonic Properties

Alloying of noble metals is lately being explored as a way to tune the optical and plasmonic properties of metal nanostructures. In order to rationally modulate properties by alloying, there is a need to fundamentally understand how the composition affects them. This work demonstrates that deep insights, useful for tailoring of noble alloy plasmonic and optical properties, can be gained by a low-cost approach based on density functional theory (DFT). We show in this work that the PBE functional, commonly used for calculation of alloy optical properties, can largely underestimate and in some cases even fail to predict a plasmonic response of an alloy. We propose the use of the GLLB-SC functional as a same-cost alternative and demonstrate it has an overall better performance than PBE for alloyed nanoparticles, thin films, and bulk alloys. The evolution of optical properties with composition range in the UV/Vis region is explained by connecting the alloy composition, band structure, and the resulting dielectric function. Additionally, an emergent property of alloying in the form of strong optical losses due to interband transitions in the IR region is identified and its origin is elucidated.

metal alloys ; nanostructures ; plasmonics ; density functional theory ; band structure ; dielectric function ; hot carriers

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