Optical Properties of Materials for Magnesium Plasmonics Described within DFT+U Approach

The most widely used and applied plasmonic materials, namely silver and gold, has limitations due to their high cost and restriction on the spectral position and shape of the plasmon resonance. This remains true for bimetallic silver–gold nanoparticles. Higher flexibility is required, in particular, for the design of broadband absorbers of light, and for this task the metals other than silver and gold are considered. In this paper we study the optical extinction spectra of alloy and composite nanoparticles containing magnesium and gold. The dielectric properties are calculated within the approximation of independent particles (IPA) based on the electronic structure obtained using density functional theory (DFT) with Hubbard correction (DFT+U). The obtained spectra of optical extinction of magnesium–gold alloy nanoparticles demonstrate that the most sensitive to the composition is the region of wavelengths below 500 nm. Simultaneously, the position of the plasmon resonance predicted by Vegard’s law is higher than obtained from accurate DFT+U based calculations. We managed to describe the experimental optical extinction spectra of the glass sample containing gold and magnesium atoms using the calculated spectra. The results points on the formation of composite nanoparticles with core of Au₃Mg alloy and shell of Au in the considered sample.