DFT Calculations Using Quantum ESPRESSO for Optical and Electronic Properties of Si Crystal

The DFT calculations were performed to study the structural, electronic and optical properties of Si. The open source computer code, Quantum ESPRESSO used is for first-principles electronic structure modeling based on density functional theory. The optimized crystal lattice constant, band gap, density of states (DOS) and band structure were calculated. The calculated value of lattice constant was in good agreement with reported value. The band gap was calculated using three different pseudo potentials. The HSE hybrid functional provided best agreement of band gap calculations with literature values. The pseudo-dielectric functions was also calculated to estimate the optical properties including refractive indices, extinction coefficients, reflectivities and absorption coefficients in the spectral energy ranges from 0 eV to 10 eV.