Search

Compton profiles (CPs) of TM2O3 (TM = Ti, V and Cr) have been measured using 100 mCi 241Am Compton spectrometer. The experimental momentum densities have been used to check the applicability of exchange-correlation energies using pure and hybrid density functional theory (DFT). Present ab-initio computations have been accomplished using the texture of Gaussian orbitals within linear combination of atomic orbitals (LCAO) scheme. Based on experimental and theoretical CPs, hybrid DFT schemes namely B3LYP and PBESOL0 have shown better performance than pure DFT (within local density and generalized gradient approximation), whereas the best agreement (through χ2 fitting of goodness) is obtained for B3LYP prescriptions. Besides Compton spectroscopy, the spin-up (↑) energy bands and density of states (DOS) have confirmed the metallic nature of all three compounds, whereas the spin-down (↓) energy bands and DOS for Ti2O3 and V2O3 have shown a peculiar semiconducting behaviour leading to their very peculiar half-metallic character. Further, higher values of charge transfer from all the 3d transition elements to O atoms, as witnessed using Mulliken's population analysis, show a dominancy of ionic nature in these oxides. Equally normalized CPs of these oxides show that the 3d electrons in oxide environment are delocalized (in real space) in the ascending sequence Cr→V→Ti, which is in contrast to their elemental-free atom environment. [ABSTRACT FROM AUTHOR]

We report systematic investigations of opto-electronic behavior of promising semiconducting chalcopyrite compounds Cu2In(Al,Ga)Se4 within the framework of density functional theory. In view to explore their possible utilization in opto-electronic devices, we have firstly performed calculations using one of the most accurate prescriptions, namely full-potential linearized augmented plane wave method. For a better accuracy, computations have been carried out using different exchange–correlation potentials including the most accurate modified Becke–Johnson potential with hybrid functional features. Computations have been performed for various electronic and optical properties such as energy bands, total and partial density of states, real and imaginary parts of dielectric tensors, absorption spectra, reflection, refraction and energy loss spectra for both chalcopyrite compounds. We have compared our data with the existing experimental and theoretical calculations for both compounds, which validates the accuracy of present computations. Both chalcopyrites are observed to have a direct band gap nature (Cu2InAlSe4: 1.14 eV and Cu2InGaSe4: 0.96 eV). Energy peaks recorded in the imaginary part of dielectric tensors are well interpreted by means of inter-band transitions. Significant intensities observed in absorption spectra within the energy range of solar spectra unambiguously depict feasibility of these compounds in optoelectronic devices. [ABSTRACT FROM AUTHOR]