Search

Abstract: An ab initio study of the band structure, density of states, topology of the electron density and the spectral features of the linear and non-linear optical properties of the Ga2AsSb chalcopyrite are presented. The lattice parameters (a, c), the internal structure parameter, u, describing the position of Ga atom and the (c/a) ratio are optimized. The covalent bonding character is predicted via analyzing the electron density at the equilibrium geometry. The linear optical properties namely the real and imaginary parts of dielectric function, reflectivity, electron energy loss function and refractive index are calculated. This compound has a large uniaxial dielectric anisotropy and a large negative birefringence. Based on the density functional theory the non-linear optical properties are calculated and their spectra are analyzed. [ABSTRACT FROM AUTHOR]

Abstract: A theoretical study of structural, electronic, linear and nonlinear optical properties of ZnIn2Te4 defect-chalcopyrite is presented using the full-potential linearized augmented plane-wave (FP-LAPW) method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA). Moreover, the Engel and Vosko GGA formalism (EV-GGA) is also used to improve the band gap results. The lattice parameters ( a , c ) and the atomic positions (x, y and z) are optimized and found in good agreements with the available experimental data. Our calculations performed for band structure and density of state show that the valence band maximum (VBM) and conduction band minimum (CBM) are located at Γ resulting in a direct energy gap of about 0.89eV for GGA and 1.20eV for EV-GGA. The linear optical properties namely, the real and imaginary parts of the dielectric function and the reflectivity spectrum are calculated. This compound possesses a considerable negative birefringence. Based on the density functional theory the nonlinear optical properties are calculated and their spectra are analyzed. [ABSTRACT FROM AUTHOR]

Abstract: The complex density functional theory (DFT) calculations of structural, electronic, linear and nonlinear optical properties for the defect chalcopyrite CdAl2Se4 compound have been reported using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the WIEN2k code. We employed the Wu and Cohen generalized gradient approximation (GGA-WC), which is based on exchange–correlation energy optimization to calculate the total energy. Also we have used the Engel–Vosko GGA formalism, which optimizes the corresponding potential for band structure, density of states and the spectral features of the linear and nonlinear optical properties. This compound has a wide direct energy band gap of about 2.927eV with both the valence band maximum and conduction band minimum located at the center of the Brillouin zone. The ground state quantities such as lattice parameters (a, c, x, y and z), bulk modulus B and its pressure derivative B′ are evaluated. We have calculated the frequency-dependent complex , its zero-frequency limit , refractive index , birefringence , the reflectivity and electron energy loss function . Calculations are reported for the frequency-dependent complex second-order nonlinear optical susceptibilities. We find opposite signs of the contributions of the 2ω and 1ω inter/intra-band to the imaginary part for the dominant component through the wide optical frequency range. [Copyright &y& Elsevier]

Abstract: The structural and elastic behaviour of the chalcopyrite SbPGa2 and SbAsGa2 crystals has been determined by means of first principles calculations using the full-potential augmented plane wave (FPLAPW) method. Ground state properties such as the lattice parameters (a, c and u), bulk modulus B, its pressure derivative B′, have been directly calculated and compared to previous experimental and theoretical results when available. We have determined the elastic parameters (C 11, C 12, C 33, C 44 and C 66), which have not been calculated and measured yet. Thermal properties, including the linear and cubic expansion coefficients and the heat capacity, have been estimated using a quasi-harmonic Debye model. To our knowledge this is the first quantitative theoretical prediction of elastic and thermal properties for these compounds and still awaits experimental confirmations. [Copyright &y& Elsevier]

We report results from first-principles density functional calculations using the full-potential linear augmented plane wave (FP-LAPW) method. The generalized gradient approximation (GGA) and the Engel-Vosko-generalized gradient approximation (EV-GGA) were used for the exchange-correlation energy of the structural, electronic, linear and nonlinear optical properties of the chalcopyrite Ga2PSb compound. The valence band maximum (VBM) is located at the Γv point, and the conduction band minimum (CBM) is located at the Γc point, resulting in a direct band gap of about 0.365 eV for GGA and 0.83 eV for EV-GGA. In comparison with the experimental one (1.2 eV) we found that EV-GGA calculation gives energy gap in reasonable agreement with the experiment. The spin orbit coupling has marginal influence on the optical properties. The ground state quantities such as lattice parameters (a, c and u), bulk modules B and its pressure derivative B′are evaluated. [ABSTRACT FROM AUTHOR]

Abstract In this study, we pay attention to electronic, bonding and optical properties of the CuGaSe 2 compound as well as in the absence and under the application of hydrostatic pressure. We conducted this study within the approach of first principles calculations based on density functional theory. Our work yielding within the mBJ potential and other approximations, provide an improved theoretical prediction of both energy band gap value and optical quantities. In addition, results based topological partition of electron density give an adequate bonding description of both bonds and related dipolar momentums. The study provides also analysis of the investigated properties under pressure. We found that the pressure promotes the use of the CuGaSe 2 compound for more photovoltaic applications. [ABSTRACT FROM AUTHOR]

DFT calculations [ABSTRACT FROM AUTHOR]