A comparative study for structural and electronic properties of single-crystal ScN

Abstract

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.

Structural and electronic properties of GaP nanowires

“…FP-LAPW method with PBE-GGA is provided by WIEN2k package [25] and successfully used before for the determination of structural and electronic properties of low dimensional systems [26,27]. FP-LAPW calculations are outlined in our previous work [28]. The parameters of FP-LAPW calculations, particularly, R MT nK MAX , G MAX , l MAX , and cutoff energy are taken to be 7, 12 Ry, 15, and À 6.0 Ry, respectively, for all WZ-and ZB-structural GaP nanowires.…”

Optical and transport measurement and first-principles determination of the ScN band gap

“…This is at the low end of previously reported values, which range from 0.9-1.5 eV from experimental studies 26,42,46,52 and 0.79-1.70 eV from theoretical investigations that go beyond the conventional local density or generalized gradient approximations. 29,42,[54][55][56][57][58][59][60][61][62] Similarly, our value of 2.07±0.05 eV for the direct transition at the X-point is at the low end of reported measured values of the direct transition determined from optical absorption, ranging from 2.03 to 3.2 eV. 2,26,34,37,40,[42][43][44][45][46][47][48] We note that our samples, similar to the published literature, also yield quite a large range of measured optical gaps, from 2.18 to 2.70 eV.…”

“…[32][33][34] However, more recent theoretical results with improved exchange correlation functionals predict a direct X-point transition of 1.82-2.59 eV and an indirect band gap of 0.79-1.70 eV. 29,42,[54][55][56][57][58][59][60][61][62] These values are consistent with the experimental ranges of 2.03-3.2 eV and 0.9-1.5 eV for the direct and indirect transitions, respectively. However, the large ranges for gap values from both experimental and theoretical studies are unsatisfactory and motivate the present investigation.…”

First-principles calculations for the structural and electronic properties of GaAs1−xPx nanowires

“…23 The parameters of FP-LAPW calculations, particularly, R MT Â K MAX , G MAX and l MAX are set to 7, 12 ffiffiffiffiffiffi ffi Ry p and 15, respectively, for all ZB-and WZ-structural GaAsP NWs. R MT values, smallest radii of the spheres around the atoms in the unit cell, are taken as 2.02, 1.94, 1.75 and 0.85 a.u.…”