Lashounda Franklin

Predictions of electronic, structural, and elastic properties of cubic InN

We present theoretical predictions of electronic, structural, and elastic properties of cubic indium nitride in the zine-blende structure (c-InN). Our ab initio, self-consistent calculations employed a local density approximation potential and the Bagayoko, Zhao, and Williams implementation of the linear combination of atomic orbitals. The theoretical equilibrium lattice constant is 5.017A, the band gap is 0.65eV, and the bulk modulus is 145GPa. The band gap is 0.74eV at an experimental lattice constant of 4.98A.

Density-functional theory band gap of wurtzite InN

We report the calculated band gap of wurtzite indium nitride. Our ab initio computations employed a local-density approximation (LDA) potential and the linear combination of Gaussian orbital formalism. The implementation of the ab initio Bagayoko, Zhao, and Williams method [Phys. Rev. B 60, 1563 (1999)] led to a LDA band gap of 0.88eV, in excellent agreement with recent experiments. We also present calculated density of states (DOS) and the electron effective mass at the bottom of the conduction band. Our DOS curves indicate that an experiment could find values of the band gap up to 2eV, depending on the sensitivity of the apparatus, the interpretation of resulting data, and associated uncertainties.

Ab-initio calculations of electronic, transport, and structural properties of boron phosphide

We present results from ab-initio, self-consistent density functional theory calculations of electronic and related properties of zinc blende boron phosphide (zb-BP). We employed a local density approximation potential and implemented the linear combination of atomic orbitals formalism. This technique follows the Bagayoko, Zhao, and Williams method, as enhanced by the work of Ekuma and Franklin. The results include electronic energy bands, densities of states, and effective masses. The calculated band gap of 2.02 eV, for the room temperature lattice constant of a = 4.5383 A, is in excellent agreement with the experimental value of 2.02 ± 0.05 eV. Our result for the bulk modulus, 155.7 GPa, agrees with experiment (152–155 GPa). Our predictions for the equilibrium lattice constant and the corresponding band gap, for very low temperatures, are 4.5269 A and 2.01 eV, respectively.

Comment on “Band gap bowing and electron localization of GaXIn1−XN” [J. Appl. Phys. 100, 093717 (2006)]

Some previous density functional theory (DFT) calculations of the band gap of wurtzite and cubic InN, before the work of Lee and Wang [J. Appl. Phys. 100, 093717 (2006)], are in agreement with the screened-exchange findings of these authors and with experiment. These previous findings point to an intrinsic capability of DFT, in the local density approximation, to correctly describe the band gap of semiconductors. These comments also discuss some recent results [Phys. Rev. B 76, 037101 (2007)] on an extensive hybridization of the In 4d and N 2s bands that is lost when the d electrons are included in the core. Our discussions in these comments indicate that when the two inherently coupled equations of DFT are both solved self-consistently, the resulting bands, including low-lying conduction ones, appear to have much more physics content than previously believed.

Calculated electronic, transport, and related properties of zinc blende boron arsenide (zb-BAs)

We present the results from ab-initio, self-consistent density functional theory (DFT) calculations of electronic, transport, and bulk properties of zinc blende boron arsenide. We utilized the local density approximation potential of Ceperley and Alder, as parameterized by Vosko and his group, the linear combination of Gaussian orbitals formalism, and the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF), in carrying out our completely self-consistent calculations. With this method, the results of our calculations have the full, physical content of density functional theory (DFT). Our results include electronic energy bands, densities of states, effective masses, and the bulk modulus. Our calculated, indirect band gap of 1.48 eV, from Γ to a conduction band minimum close to X, for the room temperature lattice constant of 4.777 A, is in an excellent agreement with the experimental value of 1.46 ± 0.02 eV. We thoroughly explain the reasons for the excellent agreement betw...

First-principles studies of electronic, transport and bulk properties of pyrite FeS2

We present results from first principle, local density approximation (LDA) calculations of electronic, transport, and bulk properties of iron pyrite (FeS2). Our non-relativistic computations employed the Ceperley and Alder LDA potential and the linear combination of atomic orbitals (LCAO) formalism. The implementation of the LCAO formalism followed the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). We discuss the electronic energy bands, total and partial densities of states, electron effective masses, and the bulk modulus. Our calculated indirect band gap of 0.959 eV (0.96), using an experimental lattice constant of 5.4166 A, at room temperature, is in agreement with the measured indirect values, for bulk samples, ranging from 0.84 eV to 1.03 ± 0.05 eV. Our calculated bulk modulus of 147 GPa is practically in agreement with the experimental value of 145 GPa. The calculated, partial densities of states reproduced the splitting of the Fe d bands to constitute the dom...

Undergraduate Research at the Timbuktu Academy and LS-LAMP at Southern University and A&M College in Baton Rouge (SUBR)

Abstract The purpose of this chapter is to describe the climate and practice of undergraduate research in selected Science and Engineering departments at Southern University and A&M College in Baton Rouge (SUBR), Louisiana, from 1994 to 2014. We briefly recall the long tradition of undergraduate research participation and the accompanying mentoring at SUBR. The establishment of the Timbuktu Academy in 1990–1991, with funding from the National Science Foundation (NSF), followed two years of review of the literature in teaching, mentoring, and learning. The paradigm and Ten Strand Systemic Mentoring model of the Academy, with a major funding by the Department of the Navy, Office of Naval Research (ONR), have sustained a research-based and practice-verified creation of a highly supportive and challenging research eco-system for selected science, technology, engineering, and mathematics (STEM) undergraduate scholars, one that integrates seamlessly education and research.

AB-INITIO CALCULATIONS OF ELECTRONIC PROPERTIES OF InP AND GaP

We present results from ab-initio, self-consistent local density approximation (LDA) calculations of electronic and related properties of zinc blende indium phosphide (InP) and gallium phosphide (GaP). We employed a LDA potential and implemented the linear combination of atomic orbitals (LCAO) formalism. This implementation followed the Bagayoko, Zhao and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW–EF). This method searches for the optimal basis set that yields the minima of the occupied energies. This search entails increases of the size of the basis set and the related modifications of angular symmetry and of radial orbitals. Our calculated, direct band gap of 1.398 eV (1.40 eV), at the Γ point, is in excellent agreement with experimental values, for InP, and our preliminary result for the indirect gap of GaP is 2.135 eV, from the Γ to X high symmetry points. We have also calculated electron and hole effective masses for both InP and GaP. These calculated properties also agree with exp...