Electronic band structure and optical parameters of spinel SnMg 2O 4 by modified Becke - Johnson potential

The electronic band structure and optical parameters of SnMg 2O 4 are investigated by the first-principles technique based on a new potential approximation known as modified Becke - Johnson (mBJ). The direct band gap values by LDA, GGA and EV-GGA are underestimated significantly as compared to mBJ-GGA, which generally provides the results comparable to the experimental values. Similarly, the present band gap value (4.85 eV) using mBJ-GGA is greatly enhanced to the previous value by EV-GGA (2.823 eV). The optical parametric quantities (dielectric constant, index of refraction, reflectivity, optical conductivity and absorption coefficient) relying on the band structure are presented and examined. The first critical point (optical absorption's edge) in SnMg 2O 4 occurs at about 4.85 eV. A strong absorption region is observed, extending between 5.4 eV to 25.0 eV. For SnMg 2O 4, static dielectric constant 1(0), static refractive index n(0), and the magnitude of the coefficient of reflectivity at zero frequency R(0) are 2.296, 1.515 and 0.0419, respectively. The optoelectronic properties indicate that this material can be successfully used in optical devices

DFT studies for optoelectronic properties of pure l-alanine and doped with Li

Structural and optoelectronic properties of the pure l-alanine (CH3CHNH2COOH) and substituted with Li in two different sites CH3CHNHLiCOOH (basic) and CH3CHNH2COOLi (acidic) are systematically investigated by the density functional theory (DFT). We have used WIEN2k and Gaussian 09W codes for structural optimization. The optimized lattice constants are found to be consistent with the experimental results. l-Alanine is a wide indirect band gap compound and hence is an attractive material for optoelectronic applications. The calculated fundamental band gaps for CH3CHNH2COOH, CH3CHNHLiCOOH and CH3CHNH2COOLi are found to be 4.85, 3.50 and 2.40 eV, respectively. Obtained band gap value of 4.85 eV for l-alanine is in coincidence with the experimental (4.67 eV) and theoretical results (4.54 and 5.07 eV). Substitution of Li with H element in COOH chain, the transition from an indirect to direct band gap has been observed in sample. Optical properties such as dielectric functions and energy loss functions are also evaluated and discussed in detail

Evaluation of magneto-optic properties of LaXPO(X = Mn, Fe, Ni) new superconductors by DFT

This article reports about the structural, electronic and magneto-optic properties of LaXPO(X = Mn, Fe, Ni) using the density functional theory (DFT) within GW, TB-mBJ, GGA and GGA + U (U = 1, 2, 3, 4 eV). The calculated ground state values such as lattice parameters, band gap, dielectric functions, absorption coefficient, refractive index, and sumrules are in favorable agreement with the previous works and the experimental data. The computed band gap for LaMnPO (up state) is 1.25 eV (experimental value is 1.3 eV) by GGA + U (U = 4 eV). These calculations predict a half-metallic character for LaFePO and LaNiPO materials. Our results show that the nature of LaMnPO compound is magnetic, and LaFePO and LaNiPO compounds are non-magnetic materials. In band structure calculations, the GGA + U (4 eV) results for LaMnPO and TB-mBJ results for LaFePO and LaNiPO are in good agreement with the experiment

Ab initio calculations of structural, optical and thermoelectric properties for CoSb 3 and ACo 4Sb 12(A = La, Tl and Y) compounds

We present the structural, optical and thermoelectric properties of unfilled and filled CoSb 3. The full potential linearized augmented plane wave (FP-LAPW) method within the generalized gradient approximation (GGA) is used to investigate the optoelectronic properties and for thermoelectric properties we have used the semi-classical Boltzmann transport theory. The calculated fundamental band gap of unfilled CoSb 3 at Γ symmetry point is 0.036 eV. Furthermore, filling of CoSb 3 by A (A = La, Tl and Y) strongly affects the optoelectronic properties and carrier concentration of this compound. The bulk modulus of the unfilled CoSb 3 is smaller than that of filled CoSb 3 with Tl and Y. The results of study predict that the filling of Tl effectively enhances the efficiency of the thermoelectric properties of CoSb 3