Theoretical approach for calculation of dielectric functions of plasmonic nanoparticles of noble metals, magnesiumand their alloys

Plasmonic nanoparticles of gold, silver, their alloys, and of the promising magnesium and its alloys with noble metals, find increasing applications due to the valuable optical properties, based on the presence of localized surface plasmon resonance (LSPR) in the spectra of optical extinction. To suggest effective synthesis routes of such nanoparticles with tunable in the wide wavelength range characteristics of LSPR, it is necessary to have a reliable approach for calculation of dielectric functions for these particles with complicated atomic architecture, which can provide the description of experimental optical spectra. Such approach is also required for the implementation of the suggested earlier original technique for the solution of the inverted problem - determination of structural parameters of particles arrays from their optical spectra. With the aim to suggest such computational procedure, calculations of dielectric functions for gold, silver, magnesium and their alloys are performed using alternative density functional theory approaches: local density approximation (LDA), generalized gradient approximation (GGA) in the form of GLLBSC functional, meta-GGA in the form of TB09 potential and Hubbard-corrected local density approximation (LDA+U). Using the calculated dielectric functions, the LSPR of nanoparticles are simulated within the T-matrix approach. We show that the application of LDA+U approach is promising for the description of optical properties of bulk samples, their alloys and nanoparticles, including particles with core-shell atomic architecture. The advantage of magnesium-gold core-shell nanoparticles as a broadband nanosized plasmonic material is illustrated.