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This contribution demonstrates density functional theory calculations on the optoelectronic properties of monoclinic CuO under high pressures up to 15 GPa. In this account, the experimentally measured indirect band gap energy value of 1.41 eV has theoretically been predicted by tuning the Hubbard parameter (U) values for the partial electronic states. The values of the Hubbard parameter correspond to UCu-3d = 8 eV and UO-2p = 4.5 eV. The electronic and optical characteristics were examined under applied pressure and the results reveal development in the band gap values with increasing pressure from 1.41 to 2.01 eV. Total and projected density of states for the adopted pressures have been provided and displayed that the major contribution in the valance and conduction bands comes from O-2p and Cu-3d electronic states, respectively. The plotted reflectivity data suggest high optical reflectivity magnitudes relatively in the ultraviolet area. The investigated systems under variant pressures manifest rather an excellent absorption coefficient in the ultraviolet area, pushing them to be employed in solar cell technologies. Our analyzed results of the wavelength-dependent electrical conductivity of the investigated materials confirm the absorptivity behavior in the ultraviolet and small part of visible region of electromagnetic waves (EMW). Finally and most importantly, our obtained results of loss functions for the entire surveyed systems reveal a slight energy loss in a range of EMW, including ultraviolet and visible regions. [ABSTRACT FROM AUTHOR]

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This contribution aims to investigate volume-dependent thermal and mechanical properties of the two most studied phases of molybdenum nitride (c-MoN and h-MoN) by means of the quasi-harmonic approximation approach (QHA) via first-principles calculations up to their melting point and a pressure of 12 GPa. Lattice constants, band gaps, and bulk modulus at 0 K match corresponding experimental measurements well. Calculated Bader's charges indicate that Mo-N bonds exhibit a more ionic nature in the cubic MoN phase. Based on estimated Gibbs free energies, the cubic phase presents thermodynamic stability higher than that detected for hexagonl, with no phase transition observed in the selected T- P conditions as detected experimentally. The elastic stiffness coefficients of MoN in hexagonal structure revealed that it is stable elastically; in contrast to the cubic structure. The temperature dependence on the bulk modulus is more profound on the dense cubic phase than on the hexagonal phase. Overall, the two considered structures of molybdenum nitride display very minimal harmonic effects, evidenced by the slight variation of thermal and mechanical properties with the increase of pressure and temperature. The optical conductivity of both phases near a zero photon energy coincides well with their metallic character inferred by their corresponding DOS curves. It is expected that the thermo-elastic properties of saturated molybdenum nitrides reported in this study will aid in the continuous pursuit to enhance their catalytic and mechanical utilizations. [ABSTRACT FROM AUTHOR]