Electronic energy structure and optical properties of In$_{4}$CdI$_{6}$ from $\textit{ab initio}$ calculations
This work presents the $\textit{ab initio}$ calculations of the electronic energy spectrum of the In$_{4}$CdI$_{6}$ compound. The study was conducted within the framework of density functional theory (DFT), using local density approximation (LDA) and general gradient approximation (GGA) pseudopotentials, and the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional. The GGA approximation was implemented using the PBE and PBEsol exchange-correlation functional. Based on the electronic energy structure, the type of the minimum band gap was determined, and an analysis of the energy level dispersion for both the valence and conduction bands was performed. Furthermore, the effective masses of electrons ($\textit{m}_{c}$) and holes ($\textit{m}_{v}$) for In$_{4}$CdI$_{6}$ were established. The energy band analysis was complemented by the calculation of the density of states (DOS). Based on the electronic energy spectrum, the real and imaginary components of the dielectric function are calculated. Using the Kramers-Kronig relations, we also derive such fundamental optical functions of In$_{4}$CdI$_{6}$ as the refractive index $\textit{n}$, and the extinction coefficient $\textit{k}$.