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In this study, an analysis of the effect of Na substitution on the electronic, structural and thermoelectric (TE) properties of the Li2CuAs material is presented. The study is performed by employing the full-potential linearized augmented plane wave plus local orbital method designed within the density functional theory. To carry out the calculations related to the band structure, generalized gradient approximation by Wu-Cohen (WC-GGA) in combination with Trans Blaha-modified Becke-Johanson mBJ (TB-mBJ) potential is employed. Our results at the level of the WC-GGA approach show that there is no bandgap, whereas, at the level of the TB-mBJ approximation, the material displays bandgap with Na substitution, which is found to be further increased with the increasing Na concentration. To understand the role of different electronic states on the bandgap structure, the total and partial densities of states are also analysed. Furthermore, the temperature effect on the Seebeck coefficient, electronic thermal conductivity, electrical conductivity, power factor and figure of merit are computed. Our obtained results of the TE properties of Li2CuAs at different Na compositions suggest that this compound is a potential candidate for thermoelectricity. [ABSTRACT FROM AUTHOR]

Tetra-strontium di-pnictide oxides Sr 4 Pn 2 O (Pn = Sb, Bi) belong to the oxypnictide-type materials attracting a lot of attention due their unique properties which are very advantageous for photovoltaic and thermoelectric applications. In spite of the fact that structural features of Sr 4 Pn 2 O (Pn = Sb, Bi) are known, however, their ability for applying in renewable energy has not been discovered yet. Therefore, in this study, the electronic structure of the two compounds was studied in detail that provides a key knowledge on understanding their optical and thermoelectric properties. The present data indicate that Sr 4 Pn 2 O (Pn = Sb, Bi) oxides have suitable band structure for photovoltaic applications with high absorption rates of 105–106 cm−1. The two compounds are also promising p-type thermoelectric materials with the figure of merit of about 0.45–0.55. Sr 4 Pn 2 O materials have strong nonlinear characteristics, making them highly promising for optical switching devices. Our research provides further insights into the features of Sr 4 Sb 2 O and Sr 4 Bi 2 O compounds besides current experimental data, demonstrating that both compounds have promising characteristics as optoelectronic materials. [ABSTRACT FROM AUTHOR]

In this work, first-principles calculations were utilised to study the structural, magnetic and electronic properties of Mn 2 PtZ (Z = V, Co) based on density functional theory (DFT). These compounds are predicted to be more stable in the Cu 2 MnAl structure and the FM ground state is energetically favourable, with magnetic moments of 4.93 and 9.04 μ B / f.u. for Mn 2 PtV and Mn 2 PtCo compounds, respectively. Additionally, the computed total magnetic moments of both compounds agree well with the Slater–Pauling rule, M T = N V - 24, and the main contribution in these magnetic moments emanates from Mn atoms for both materials. Through the results on the spin-polarised electronic properties (band structures and densities of states), it is found that both alloys reveal a complete half-metallic (HM) character with a half-metallic gap using GGA + U + TB-mBJ approximation. [ABSTRACT FROM AUTHOR]

Abstract We report the results of the FP-APW + lo calculations of the structural, electronic, optical and thermo-electric properties of the CdY 2 Ch 4 (Ch = S, Se) compounds under hydrostatic pressure effect. The calculated ground state properties agree well with the available experimental data. The investigated materials are semiconductors, with direct band gaps (Γ- Γ) of approximately 2.18 eV, 1.53 eV for CdY 2 S 4 and CdY 2 Se 4 , respectively, using GGA-TB-mBJ approximations. Under external pressure up to 20 GPa, both compounds show a linear decrease of energy gaps against pressure. Moreover, our calculated optical spectra over photon energies ranging from 0 to 20 eV suggest that CdY 2 Ch 4 (Ch = S, Se) spinel compounds express a strong response in the energy range between the visible light and extreme UV regions, highlighting their possible application in the optoelectronic devices. Furthermore, the calculated thermoelectric properties indicate that both the CdY 2 S 4 and CdY 2 Se 4 compounds show interesting thermoelectric properties. Highlights • Electronic, optical and thermoelectric properties for CdY2X4 (X = S, Se) compounds are investigated for the first time. • The electronic calculation reveals a semiconducting nature of these compounds. • Both compounds show a strong response in visible light and extreme UV regions which make them potential candidate for optoelectronic devices. • Both the CdY2S4 and CdY2Se4 compounds show attractive thermoelectric properties [ABSTRACT FROM AUTHOR]

We have studied the structural, optical, electronic and thermoelectric properties of the CaCd 2 X 2 (X = P, As) compounds by using the full-potential augmented plane wave plus local orbitals method (FP-APW + lo). The exchange-correlation potential was treated using both the gradient generalized approximation (WC-GGA) and local density approximation (LDA). The estimated structural parameters, including the lattice parameters and internal coordinates agree well with the available experimental data. Our computed band structure shows that both studied compounds are semiconductors, with direct band gaps (Γ-Γ) of approximately 1.78 eV and 1.2 eV for CaCd 2 P 2 and CaCd 2 As 2 , respectively, using GGA-TB-mBJ approach. The calculated optical spectra reveal a strong response of these materials in the energy range between the visible light and extreme UV regions, making them a good candidate for optoelectronic devices. Thermoelectric parameters, such as thermal conductivity, electrical conductivity, Seebeck coefficient, power factor and figure of merit were calculated. We note that both the CaCd 2 P 2 and CaCd 2 As 2 compounds show promising thermoelectric properties. [ABSTRACT FROM AUTHOR]

The orthorhombic CaM 2 S 4 (M = Sc, Y) structures were investigated in the present work by first-principles calculations. CaM 2 S 4 (M = Sc, Y) compounds are found to be mechanically stable with the anisotropic elastic constants that make them to be stable with respect to uniaxial deformation (Young's moduli are 73.724 and 57.441 GPa for CaSc 2 S 4 and CaY 2 S 4 , respectively) but easy to be undergone to shear deformation (Poisson's ratios are 0.352 and 0.371 for CaSc 2 S 4 and CaY 2 S 4 , respectively). Due to their relatively small direct energy band gaps (1.89 eV for CaSc 2 S 4 and 2.26 eV for CaY 2 S 4), the two compounds are intriguing candidates for long-wave transparency applications. The high hybridization degree of Ca-d, Y/Sc-d and S-p orbitals results in a wide energy range between the valence highest band and the conduction lowest band enabling these compounds to interact actively with visible and ultra-violet waves. The high absorption rate of 12–18 × 105 cm−1 and good hole-electron separation make CaM 2 S 4 (M = Sc, Y) compounds to consider them good candidates for optoelectronic materials. Moreover, CaM 2 S 4 (M = Sc, Y) compounds show good ability in the process of photo-driven photocatalyst water splitting. [ABSTRACT FROM AUTHOR]

[Display omitted] • The electronic and photoelectrochemical properties of La/Ni-doped SrTiO 3 were investigated. • La-doped SrTiO 3 exhibits n-type conduction with a bandgap value of 2.924 eV. • Ni-doped SrTiO 3 behaves as a p-type semiconductor with a bandgap value of 1.337 eV. • La/Ni-doping results in a lower recombination rate compared to pure SrTiO 3. • The Sr 0.945 La 0.055 TiO 3 alloy has a suitable band edge position for water splitting. • SrNi 0.055 Ti 0.945 O 3 exhibits the ability for only water oxidation. The study of the physical properties of doped SrTiO 3 materials using the full potential linearised augmented plane wave (FP-LAPW) technique has revealed interesting findings. In particular, we explored the semiconducting behavior of La- and Ni-doped SrTiO 3 alloys through band structure calculations. The results showed that Sr 0.945 La 0.055 TiO 3 exhibited n-type semiconducting behavior with a bandgap of approximately 2.924 eV. In contrast, Ni-doped SrTiO 3 demonstrated a reduction in band gap value of around 1.337 eV due to the emergence of 3 d -Ti states in the middle of the SrTiO 3 band gap. This unique characteristic makes SrNi 0.055 Ti 0.945 O 3 a promising candidate for optoelectronic devices. Furthermore, the photo-electrochemical analysis revealed that Sr 0.945 La 0.055 TiO 3 has a band edge position that is suitable for photocatalytic water splitting, making it a more attractive candidate for this application compared to SrNi 0.055 Ti 0.945 O 3. These findings have important implications for the design and development of novel materials with specific properties for a range of technological applications. [ABSTRACT FROM AUTHOR]