Investigation of the electronic, optical, elastic, mechanical and vibrational properties of CuI using HSE03

Ab Initio density functional theory (DFT) simulations have been employed to systematically explore the electronic, optical, elastic, mechanical and vibrational properties. In this study, we revealed that [Formula: see text]-CuI has a wide direct bandgap energy of 3.21 eV, is pure covalent and brittle. We also found that the core level is made up of I s electron orbitals, the valence band is constructed with I p orbitals, and the Cu s orbital states mainly contribute to the conduction band minimum (CBM). The reflectivity of CuI is reported to be low (35.9% for the light reflected), showing high material absorption. A high absorption coefficient of [Formula: see text] is also reported. The elastic and mechanical properties can further confirm the mechanical stability of the CuI system, derived from DFT-calculated elastic constants and phonon dispersion from density functional perturbation theory (DFPT) calculations.