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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]

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]

γ-MnS thin films were prepared on glass substrate by spray pyrolysis method at 280 °C. The optical constants and thickness of the films were extracted using the pattern search optimization technique in combination with a seed preprocessing procedure (spPS). Refractive index dispersion of the films was analyzed by using the concept of the single oscillator model. The values of the oscillator energy, E0, and the dispersion energy, Ed, were determined as 8.83 eV and 5.65 eV, respectively. The analysis of the optical properties of the γ-MnS film showed a direct transition with energy band gap of 2.74 eV. Utilizing Hall Effect measurement, we have determined values of the resistivity p which equals to 1150 Ocm. The positive value of hall coefficient showed a p-type in nature of the obtained thin film. The maximum of photocurrent density estimated by Yablonovitch limit is equal to 46 mA/cm2. [ABSTRACT FROM AUTHOR]

A higher quality and a nearly stoichiometric composition of Cd0.5Zn0.5Te have been successfuly grown on glass substrate by vacuum evaporation technique. The composition and structural studies are investigated by energy dispersive X-ray analysis, SEM, and X-Ray diffraction. Film optical constants are determined from transmittance measurments at normal light incidence in the spectral range (500-2500nm). The presence of interference fringes and of a sharp absorption edge are indicatives of a very good optical quality. Analysis of the refractive index n(λ), of the induced absorption(hv) and the determination of the energy bandgap Eg, are then given from the acquisition of the transmission data. Comparaison with previous works on films prepared by other techniques confirms a better quality of our films prepared at low cost. [ABSTRACT FROM AUTHOR]

Abstract: We have performed R&D project on methanol synthesis from CO2 and hydrogen in order to contribute to CO2 mitigation. High-performance Cu/ZnO based multicomponent catalysts were developed. The roles of metal oxides contained in Cu/ZnO-based catalysts were classified into two categories: (1) Al2O3 or ZrO2 improves the dispersion of copper particles in the catalyst; (2) Ga2O3 or Cr2O3 increases the activity per unit copper surface area of the catalyst. The long-term stability of Cu/ZnO-based catalysts during methanol synthesis from CO2 and hydrogen was improved by adding a small amount of silica to the catalysts. Silica added to the catalysts suppressed the crystallization of ZnO contained in the catalysts. The catalysts were found to be highly active and extremely stable in methanol synthesis from CO2 and hydrogen. In the next step, a bench plant with a capacity of 50 kg day−1 of CH3OH, which was equipped with facilities for recycling unreacted gases and gaseous products, was successfully operated. The purity of crude methanol produced was 99.9 wt%, whereas the purity of crude methanol produced from syngas in a present-day commercial plant was reported as 99.6 wt%. [Copyright &y& Elsevier]

Abstract: First-principles study of the ground-state properties and the stability of Ca1−x Zn x O solid solutions is presented using the full-potential linearized augmented plane wave (FP-LAPW) method. We employed the local density approximation (LDA) to the exchange-correlation potential. It is found that the structural parameters, i.e., lattice constants and bulk moduli deviate from the linear function of the composition x. We determined the equation of state of the alloys and showed an increasing compressibility function of composition. The formation energy is viewed as an energetic balance between pure structural constraints and quantum chemical effects. Thus, a phase separation over the whole range of concentration is expected. The origin of the miscibility gap has a chemical nature. Also, the thermodynamic stability of the alloys was investigated. [Copyright &y& Elsevier]

Abstract: First-principles study of the ground-state properties and the stability of Cd1−x Zn x O solid solutions are presented using the full-potential linearized, augmented plane-wave (FP-LAPW) method in combination with the local density approximation (LDA). It is found that the structural parameters, i.e. lattice constants and bulk moduli strongly deviate from the linear function of the composition . The equation of state of the alloys is determined and an increasing compressibility function of composition is found. The formation energy is viewed as an energetic balance between pure structural constraints and quantum chemical effects. Our calculations yield the prediction of phase separation over the whole range of concentration. This trend was explained to have a structural nature caused by the high lattice mismatch. Also, the thermodynamic stability of the alloys has been investigated. [Copyright &y& Elsevier]

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]