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This study examines the physical characteristics of Co2Te3O8 in the spiroffite structure using an ab initio approach. The optimization of the Co2Te3O8 structure, in both nonmagnetic and magnetic states, indicates that the magnetic state is more stable than the non-magnetic one. Thermodynamic properties under various temperatures and pressures, calculated via the quasi-harmonic approximation, reveal that the specific heat capacity of spiroffite Co2Te3O8 conforms to the Debye model and satisfies the Dulong and Petit limits. The electrical, magnetic, and optical properties of Co2Te3O8 are investigated using the GGA and TB-mBJ approximations. Analysis of the density of states and the band structure indicates that spiroffite Co2Te3O8 exhibits semiconductor characteristics in both the spin up and spin down channels. The study is extended to apply hydrostatic pressure to assess the electronic and magnetic properties of both unstrained and strained structures of Co2Te3O8. It is found that within the investigated pressure range (0–15 GPa), no structural changes are observed. Furthermore, a slight decrease in the spin up gap is noted, while no appreciable changes are observed in the spin down gap. Moreover, the investigation into the spin-polarized thermoelectric properties of the material reveals that it achieves a high figure of merit, approximately 0.99, across broad temperature spectra. This performance highlights its suitability as a candidate for thermoelectric power generation. Finally, optical properties calculations on spiroffite Co2Te3O8 reveal efficient absorption in the ultraviolet region. [ABSTRACT FROM AUTHOR]

The full potential-linearized augmented plane wave (FP-LAPW) method is implemented in WIEN2K code to calculate the indirect energy gap (r-X) using density functional theory. The Engel-Vosko generalized gradient approximation (EVGGA) and modified Becke-Johnson (mBJ) formalisms are used to optimize the corresponding potential for energetic transition and optical properties calculations of PbS and PbTe compounds as a function of quantum dot diameter and are used to test the validity of our model of quantum dot potential. The refractive index and optical dielectric constant are investigated to explore best applications for solar cells. The calculated results are in agreement with other experimental and theoretical data. Key words: quantum dot, lead chalcogenides, optical properties, refractive index, optical dielectric constant. La methode de calcul FP-LAPW, ou l'approximation linearisee en ondes planes ameliorees a potentiel complet, est implementee dans le logiciel WIEN2K pour calculer la bande interdite indirecte (T-X) dans le cadre de la theorie de la fonctionnelle de densite. Nous utilisons l'approximation du gradient generalise de Engel-Vosko (EVGGA) et les formalismes modifies de Becke- Johnson (mBJ) afin d'optimiser le potentiel correspondant pour les calculs de transition en energie et des proprietes optiques des composes PbS et PbTe en fonction du diametre du point quantique, afin de valider notre modele de potentiel du point quantique. Nous etudions l'indice de refraction et la constante dielectrique aux frequences optiques, dans le but de determiner les meilleures applications aux cellules solaires. Nos calculs sont en bon accord avec d'autres donnees experimentales et theoriques. [Traduit par la Redaction] Mots-cles : point quantique, chalcogenures de plomb, proprietes optiques, indice de refraction, constante dielectrique aux frequences optiques. PACS Nos.: 81.07.Ta, 74.70.Xa, 74.25.Gz, 78.20.Ci, 78.20.Ci., 1. Introduction The IV-VI semiconductors are among the most interesting materials in solid-state physics. The most widely studied compounds in this group are PbS and PbTe. These materials have narrow [...]

Technological development cannot take place without a deep knowledge of materials and their physical properties. Complex oxides constitute a family of materials characterized by specific characteristics prompting them for potential technological applications. The results of a theoretical study related to the structural, thermodynamic, electronic, optical, and magnetic properties of the Dy2Be2GeO7 complex oxide are presented. The current study is accomplished using the "Full Potential (FP) Linearized (L) Augmented Plane Wave Plus Local Orbitals (APW + lo)" formalism as incorporated in the WIEN2k computational code in the "density functional theory" framework. To approximate the exchange and correlation effects, the PBE-GGA formalism of the "generalized gradient approximation" is used. Furthermore, "Tran-Blaha modified Becke–Johnson potential" is used to better describe the electronic structure. The equilibrium structural parameters are in good agreement with the corresponding measured data reported in the literature. The thermodynamic properties of the title compounds are explored via the quasi-harmonic approximation over temperature and pressure ranges from 0 to 700 K and 0 to 10 GPa, respectively. The electronic properties are determined with spin-polarized inclusions. Finally, the optical properties are examined with a detailed discussion of different optical parameters, including dielectric function, absorption coefficient, optical conductivity, reflectivity, and refractive index spectra. The Dy2Be2GeO7 complex oxide with a non-centrosymmetric tetragonal structure shows a negative birefringent, therefore it is a possible candidate for applying to the birefringent field and nonlinear optical process. To our best knowledge, the current study is the first effort to explore the physical characteristics of the considered complex oxide. [ABSTRACT FROM AUTHOR]

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]

In this study, the full potential linearized augmented plane wave method with the GGA approximation was employed to study the structural, elastic, electronic and thermal properties of the novel intermetallic REPt 4 In 4 (RE = Eu, Gd, Tb, Dy, Ho) compounds. Our findings demonstrate that the equilibrium lattice parameters are in good agreement with the available experimental measurements. The elastic constants ( C ij ) were also calculated to understand the mechanical properties and structural stability of the compounds. Furthermore, the density of states and the charge density distributions of the compounds were calculated to understand the nature of the bonding in the material. Our analysis of the calculated values of the Poisson’s ratio and the B/G ratio shows their ductile structure. Additionally, the temperature-dependent thermodynamic parameters are computed by the quasi-harmonic Debye model in the range of 0–600 K, where the primitive cell volume and thermal expansion coefficients have been obtained successfully. Consequently, this study on the structural, elastic, bonding and thermal properties of REPt 4 In 4 intermetallic compounds demonstrate that these compounds can be used as potential candidates in the domain of energy storage and electronic devices. [ABSTRACT FROM AUTHOR]

The structural, elastic, and electronic properties of rare earth intermetallic RNiPb (where R = Ho, Lu, and Sm) compounds were investigated with the density functional theory (DFT) calculations. The calculations are performed using the full potential-linearized augmented plane wave (FP-LAPW) method within the framework of local density approximation (LDA). The calculated values of the equilibrium lattice constants were in agreement with the available experimental values. The elastic constants ( C ) were also calculated to understand the mechanical properties and structural stability of the compounds. Furthermore, the density of states and the charge density distributions of the compounds were calculated to understand the nature of the bonding in the material. The calculated results are in accordance with the available data in the literature. [ABSTRACT FROM AUTHOR]