Thermoelectric properties of SbNCa3 and BiNCa3 for thermoelectric devices and alternative energy applications

Thermoelectric properties of two antiperovskites SbNCa3 and BiNCa3 are calculated using first principles calculations. High values of Seebeck coefficients are observed for these materials. Electrical and thermal conductivities are also calculated. Increase in thermal conductivity and decrease in electrical conductivity are found with increasing temperature. The maximum values of thermal conductivity are 92×1014 W/m K s and 88×1014 W/m K s for SbNCa3 and BiNCa3 respectively at a temperature of 900 K. The peak values of 5×1020/Ω m s and 5.2×1020/Ω m s are achieved for n-type SbNCa3 and BiNCa3 respectively at a temperature of 300 K. Figure of merit is achieved for these materials at room temperature which shows that these materials can be useful for thermoelectric devices and alternative energy sources.Scopu

Electronic, magnetic and optical properties of reduced hybrid layered complex Ni(pyz)V4O10 (pyz=C4H4N2) by first-principles

This article reports the electronic, structure, magnetic and optical properties of reduced hybrid layered complex Ni(pyz)V4O10 (pyz=C4H4N2) studied by employing density functional theory with local density approximation (LDA), generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof-96 (PBE) and modified Becke-Johnson (mBJ) exchange-correlation potential and energy. The band structure and density of states of these compounds are also presented. The total density of states (DOS) for up and down spin states clearly split, which means that the exchange interaction causes the ordered spin arrangement. PBE-mBJ calculation reveals a wider band gap in spin down state, which shows a half-metallic electronic character at the equilibrium state. The spin-polarized calculations indicate metallic nature in orthorhombic crystalline phase. It is also noted that the optical conductivity for PBE-mBJ is larger than that of LDA and PBE-GGA. Furthermore, the results show a half-metallic ferromagnetic ground state for Ni(pyz)V4O10 in PBE-mBJ potential. The present results suggest Ni(pyz)V4O10 compound as a potential candidate for the future optoelectronic and spintronic applications.clos

Optoelectronic properties of XIn2S4 (X = Cd, Mg) thiospinels through highly accurate all-electron FP-LAPW method coupled with modified approximations

We report the structural, electronic and optical properties of the thiospinels XIn2S4 (X = Cd, Mg), using highly accurate all-electron full potential linearized augmented plane wave plus local orbital method. In order to calculate the exchange and correlation energies, the method is coupled with modified techniques such as GGA+U and mBJ-GGA, which yield improved results as compared to the previous studies. GGA+SOC approximation is also used for the first time on these compounds to examine the spin orbit coupling effect on the band structure. From the analysis of the structural parameters, robust character is predicted for both materials. Energy band structures profiles are fairly the same for GGA, GGA+SOC, GGA+U and mBJ-GGA, confirming the indirect and direct band gap nature of CdIn2S4 and MgIn2S4 materials, respectively. We report the trend of band gap results as: (mBJ-GGA) > (GGA+U) > (GGA) > (GGA+SOC). Localized regions appearing in the valence bands for CdIn2S4 tend to split up nearly by approximate to 1 eV in the case of GGA+SOC. Many new physical parameters are reported that can be important for the fabrication of optoelectronic devices. Optical spectra namely, dielectric function (DF), refractive index n(omega), extinction coefficient k(omega), reflectivity R(omega), optical conductivity sigma(omega), absorption coefficient alpha(omega) and electron loss function are discussed. Optical's absorption edge is noted to be 1.401 and 1.782 for CdIn2S4 and MgIn2S4, respectively. The prominent peaks in the electron energy spectrum situated between 15 eV and 23 eV for the herein studied materials indicate a transition from metallic to the dielectric character.close0