A comparative study by FP-LAPW calculations based on DFT within LDA, PBE-GGA, EVex-PWco-GGA, and EVex-GGA-LDAco schemes is introduced for the structural and electronic properties of ScN in RS, ZB, WZ, and CsCl phases. According to all approximations used in this work, the RS phase is the stable ground state structure and makes a transition to CsCl phase at high transition pressure. While PBE-GGA and EVex-PWco-GGA's have provided better structural features such as equilibrium lattice constant and bulk modulus, only EVex-PWco-GGA and EVex-GGA-LDAco's have given the non zero, positive indirect energy gap for RS-ScN, comparable with the experimental ones. The indirect band gap of ScN in RS phase is enlarged to the corresponding measured value by EVex-PWco-GGA+U SIC calculations in which the Coulomb self and exchangecorrelation interactions of the localized d-orbitals of Sc have been corrected by the potential parameter of U. The EVex-PWco-GGA calculations have also provided good results for the structural and electronic features of ScN in ZB, WZ, and CsCl phases comparable with the theoretical data available in the literature. EVex-PWco-GGA and EVex-PWco-GGA+U SIC schemes are considered to be the best ones among the others when the structural and electronic features of ScN are aimed to be calculated by the same exchange-correlation energy approximations.
The stability and electronic properties of the hexagonal, trigonal and rectangular cross-sectional GaP nanowires in wurtzite (WZ) phase are investigated using full potential linear augmented plane waves method. The rectangular cross-sectional nanowires are found more stable than the hexagonal and trigonal ones. The indirect bandgap structure of the nanowires is transformed into the direct bandgap one at a critical size connected to the geometry of the cross-section. The energy bandgap of the nanowires in the same cross-sectional group is enlarged by the quantum size effect. The effective carrier masses in the nanowires, calculated to be larger than those in bulk GaP, are found to slightly increase with the decrease in the size of the nanowires in the same cross-sectional groups. The mechanical strain effect on the electronic band structure is investigated for the rectangular GaP nanowires under the uniaxial and lateral strains. It is found that the indirect bandgap structures of the rectangular nanowires are transformed into the direct bandgap ones by the uniaxial high compression strains. It is also found that this transformation can be triggered by small uniaxial tensile and high lateral tensile strains in addition to the effect of size increase. The energy bandgap of the rectangular nanowires is determined to be narrowed by the uniaxial/lateral strains. It is obtained that the small rectangular nanowire is in the indirect bandgap structure for all the lateral strains and the larger one can be transformed into the direct bandgap structure more easily by the [Formula: see text]-directional lateral tensile strains compared to the [Formula: see text]-directional ones. The effective electron and hole masses are found to be reduced by the uniaxial highest tensile and compression strains of this work. It is determined that the lateral strains are not effective in making the electrons of the nanowires more mobile, but the [Formula: see text]-directional lateral high tensile strains make the holes more mobile by reducing the effective hole mass in the small rectangular nanowire.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.