Real-time time-dependent density functional theory for the dielectric function of plasmonic materials

We use DFT+U to improve upon local and semi-local functionals which tend to underestimate onset of the interband transitions. DFT+U is less computationally expensive than hybrid functionals and the GW method. While DFT+U can be applied empirically by tuning the Hubbard U to align with an experimental observable, we apply the fully ab initio approach, the ACBN0functional.

The ACBN0 functional is found to overestimate the interband onset which suggested the introduction of the short-range ACBN0 functional. The dielectric function calculated using the short-range ACBN0 functional is in good agreement with both empirical DFT+U and experiments for copper, silver and gold. The short range-ACBN0 functional is shown to reduce to the local density approximation (LDA) in titanium nitride, as LDA is a good approximation for titanium nitride.

The protocol presented for calculating the dielectric function accurately predicts the plasmonic properties and is computationally inexpensive, with potential applications in material discovery for plasmonic devices.<br>