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In this study, first-principles investigations were performed using the full-potential linearized augmented plane-wave method of the structural and optoelectronic properties of thorium germinate (ThGeO 4 ), a high-K dielectric material. Under ambient conditions, the structural properties calculated for ThGeO 4 in the zircon phase were in excellent agreement with the available experimental data. Furthermore, using the modified Becke -Johnson correction method, the calculated band gaps and optical constants accurately described this compound. Finally, the thermal properties were predicted over a temperature range of 0–700 K and pressures up to 11 GPa using the quasi-harmonic Debye model, where the variations in the heat capacity, primitive cell volume, and thermal expansion coefficients were determined successfully. [ABSTRACT FROM AUTHOR]

Semi-Heusler materials are intensively investigated due to their potential use in diverse applications, such as in spintronics and green energy applications. In this work, we employ the density functional theory to calculate the structural, electronic, elastic, thermal and optical properties of the VRuSb, NbRuSb and TaRuSb semi-Heusler compounds. The calculated results for the lattice constants, bulk moduli and their corresponding pressure derivative values are in fairly good agreement with previous works. In addition, besides the local density approximation, the modified Becke-Johnson exchange potential is also used to improve the value of the band gaps. The bonding nature reveals a mixture of covalent and ionic bonding character of the VRuSb, NbRuSb and TaRuSb compounds. Furthermore, the elastic constants ( C) and the related elastic moduli confirm their stability in the cubic phase and demonstrate their ductile nature. We also analyze the influence of the pressure and temperature on the primitive cell volume, heat capacity, volume expansion coefficient, and Debye temperature of the semi-Heusler compounds. Additionally, we investigate the optical properties, such as the complex dielectric function, refractive index, reflectivity, and the energy loss function. [ABSTRACT FROM AUTHOR]

The structural, elastic, electronic, optical, and thermodynamic properties of the $$\hbox {ZnAl}_{2}\hbox {S}_{4 }$$ compound are calculated in the frame work of the density functional theory where the calculated structural parameters are found to be in good agreement with the experimental data and other theoretical calculations. The calculations show that the material is elastically stable and isotropic. Furthermore, the calculated band gap is observed to be wide and direct and is comparable with earlier experimental data as well as with other theoretical calculations; hence, it is an optically active material for optoelectronic applications. In addition, the compound is found to have mixed ionic and covalent bonding nature. The optical nature of the compound is described in terms of the complex dielectric function, complex refractive index, reflectivity, and energy loss function. On the other hand, variation of the unit cell volume, bulk modulus, heat capacity, and Debye temperature are described as a function of temperature at different pressures for the $$\hbox {ZnAl}_{2}\hbox {S}_{4}$$ compound. [ABSTRACT FROM AUTHOR]

Highlights: [•] The tetragonal NaZnP has brittle nature. [•] The Cu2Sb-type phase of NaZnP is a direct band gap semiconductor. [•] The TB-mBJ approximation yields larger fundamental band gaps. [•] The bonding in Cu2Sb–NaZnP is of covalent-ionic character. [•] High reflectivity (60%) and refractive index (3.9) are observed for the compound. [ABSTRACT FROM AUTHOR]

The mechanical, optoelectronic, and thermodynamic properties of carbon silicon nitride spinel compound have been investigated using density functional theory. The exchange-correlation potential was treated with the local density approximation (LDA) and the generalized gradient approximation of Perdew-Burke and Ernzerhof (PBE-GGA). In addition, the Engel-Vosko generalized gradient approximation (EV-GGA) and the modified Becke-Johnson potential (TB-mBJ) were also applied to improve the electronic band structure calculations. The ground state properties, including lattice constants and bulk modulus, are in fairly good agreement with the available theoretical data. The elastic constants, Young's modulus, shear modulus, and Poisson's ratio have been determined by using the variation of the total energy with strain. From the elastic parameters, it is inferred that this compound is brittle in nature. The results of the electronic band structure show that CSi2N4 has a direct energy band gap ( Γ- Γ). The TB-mBJ approximation yields larger fundamental band gaps compared to those of LDA, PBE-GGA, and EV-GGA. In addition, we have calculated the optical properties, namely, the real and the imaginary parts of the dielectric function, refractive index, extinction coefficient, reflectivity, and energy loss function for radiation up to 40.0 eV. Using the quasi-harmonic Debye model which considers the phononic effects, the effect of pressure P and temperature T on the lattice parameter, bulk modulus, thermal expansion coefficient, Debye temperature, and the heat capacity for this compound were investigated for the first time. [ABSTRACT FROM AUTHOR]

Bonding nature as well as structural, optoelectronic and thermal properties of the cubic XMg204 (X = Si, Ge) spinel compounds have been calculated using a full-potential augmented plane-wave plus local Orbitals (FP-APW+lo) method within the density functional theory. The exchange-correlation potential was treated with the PBE-GGA approximation to calculate the total energy. Moreover, the modified Becke-Johnson po-tential (TB-mBJ) was also applied to improve the electronic band structure calculations. The computed ground-state parameters (a, B, B' and u) are in excellent agreements with the available theoretical data. Calculations of the electronic band structure and bonding properties show that these compounds have a direct energy band gap (T -- F) with a dominated ionic character and the TB-mBJ approximation yields larger fundamental band gaps compared to those obtained using the PBE-GGA. Optical properties such as the complex dielectric function ε(ω), reflectivity R(ω) and energy loss function L(ω), for incident photon energy up to 40 eV, have been predicted. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the effects of pressure P and temperature T on the thermal expansion coefficient, Debye temperature and heat capacity for the considered compounds are investigated for the first time. [ABSTRACT FROM AUTHOR]

In this study, an investigation of the structural stability, elastic, optoelectronic, thermoelectric, optical thin-film coating, and thermodynamic properties of K 2 Ag(Ga/In)Br 6 (lead-free halide double perovskites, HDPs) was performed using first-principles calculations. The optimized structural parameters are in good agreement with the available data. Furthermore, Goldsmith's tolerance factor indicates an ideal value for both double perovskites, ensuring the structural stability of the cubic perovskites, and the elasticity parameters were analyzed to ensure the mechanical stability of the cubic phase. Direct and reduced band gaps of 0.4524 eV and 1.064 eV with semiconductor behavior are found for K 2 AgGaBr 6 and K 2 AgInBr 6 , respectively, through adoption of the modified Becke–Johnson potential scheme. The absorption coefficient, refractive index, and dielectric function, as some of the optical properties, in addition to the optical thin-film properties, are well discussed, and the values suggest that these materials are promising candidates for different devices, such as optoelectronic and photovoltaic energy devices. In terms of the thermodynamics, the HDPs display favorable characteristics across various temperature and pressure ranges. Additionally, we assessed the thermoelectric properties, considering the power factor, Seebeck coefficient, thermal and electronic conductivities, and figure of merit. The current predictions suggest that these lead-free halide double perovskites have strong potential for application in thermoelectricity and photovoltaics. [ABSTRACT FROM AUTHOR]

Lead-free double halide perovskites like Rb 2 Ag(Ga/In)Br 6 have demonstrated themselves potential candidates in solar cell research owing to their environmental friendliness, stability, and exceptional performance. This study comprehensively analyzes the structural, mechanical, optoelectronic and optical coating features, as well as thermodynamic and thermoelectric properties of two Rb 2 AgGaBr 6 and Rb 2 AgInBr 6 compounds. Using the Wien2k code with GGA + mBJ exchange-correlation potentials, we confirm their structural stability in cubic phase Fm-3m and identifying them as direct band gap semiconductors (Γ → Γ) of 0.38 eV and 1.0644 eV, respectively. Then, optical analysis reveals broad absorption bands across visible and ultraviolet wavelengths, making them suitable for photovoltaic absorbers. Finally, the thermoelectric investigations under varying temperatures show favourable properties, such as a high Seebeck coefficient with poor electronic thermal conductivity. This also yields exceptional value (0.96 and 0.994 for Rb 2 AgGaBr 6 , Rb 2 AgInBr 6 , respectively) of figure of merit (ZT) at room temperature and chemical potential μ - μ 0 = - 0.09eV near the Fermi energy level, enhancing their potential for thermoelectric applications. These findings underscore the versatility and promising future of Rb 2 Ag(Ga/In)Br 6 as important semiconductors processing for optoelectronic, thermoelectric, and mechanical devices. [ABSTRACT FROM AUTHOR]

To find a seemly solution to the problems of efficiency dependency of the hybrid PV/TE devices, on important factors like "high-absorbance with high-ZT materials" and improving the performance of existing devices, are essential research topics nowadays. In this regard, we report here optical coating, and thermoelectric features of the kesterite-structured Ag 2 CdSnS 4 and Ag 2 CdSnSe 4 compounds. These investigations are performed at the level of "full-potential linearized augmented plane wave plus local orbital method, FP-L(APW + lo)" framed within the "density functional theory (DFT)" method comprised with relativistic effects. Our study of the optical coating shows that both the investigated materials have a good level of absorbance (A), approximately 80% in the visible part of the spectra. Further, we found that the magnitude of reflectance (R) of the Ag 2 CdSnX 4 (X = S, Se) thin films increase with increasing film thickness, while the response of the transmittance (T) spectra is reverse to it. These results are corroborated by the study of the transport properties by employing the Boltztrap code, and correspondingly electrical conductivity, Seebeck coefficient, electronic thermal conductivity as well as the figure of merit parameters were evaluated and analyzed as a function of the chemical potential for both investigated compounds at five values of the temperatures. Hence our obtained results show that both the investigated semiconductor materials exhibit strong potential for the application of hybrid PV/TE systems. • Some Physical properties for the Ag 2 CdSnX 4 (with X = S, S e) are investigated. • The calculated ground states properties for Ag 2 CdSnX 4 (with X = S, S e) compare well with the available data. • The electronic properties calculation reveals that the compounds are direct band gap semiconductors. • The optoelectronic and thermoelectric characteristics for Ag 2 CdSnX 4 (with X = S, S e) are investigated for the first time. [ABSTRACT FROM AUTHOR]

First principles calculations were carried out on the SrMoO 4 compound which has been of interest owing to its technologically important physical properties. The structural, electronic, optical and thermal properties of this compound have been investigated under low pressure (LP) through the full potential linearized augmented plane wave method (FP-LAPW) within the framework of density functional theory. It is found that the phase transition from zircon to scheelite type structure occurs at negative pressure. The calculated ground state properties in scheelite structure are found to be in good accord with previously published data. Using the recently developed Tran Blaha-modified Becke Johnson approach, we have also studied the electronic band structure of this compound which shows the semiconducting behavior with a direct band gap of 4.30 eV in the scheelite phase, whereas the band gap is found to be 2.18 eV in the zircon phase. Various thermodynamic properties including the thermal volume expansion coefficient and heat capacities at constant volumes and pressures were calculated via the quasi-harmonic Debye model at different temperatures (0–1000 K). Furthermore, optical properties such as complex dielectric function, refractive index, and reflectivity spectra of the titled compound were studied for incident electromagnetic waves in an energy range up to 16 eV. The contributions to various transitions peaks in the optical spectra are analyzed and discussed with the help from the energy dependent imaginary part of the dielectric function. [ABSTRACT FROM AUTHOR]

Full potential linearized augmented plane wave method within the framework of density functional theory was applied to calculate the structural, elastic, electronic, thermoelectric and optical properties of Mg 2 X (X=Si, Ge, Sn, Pb) compounds. Exchange-correlation effects were treated using generalized gradient approximation and modified Becke–Johnson technique. Calculated structural parameters were found in good agreement to the experimental data. With the pressure application, the lattice constant decreased while the bulk modulus increased. Brittleness and ductility of these compounds were interpreted via the calculated elastic constants. The optical properties like complex dielectric function, refractive index, reflectivity, and optical conductivity were investigated in the pressure range 0–10 GPa. Very high reflectivity in a wide energy range indicates the usefulness of these materials as a shield from high energy radiations. In addition, the thermopower of the materials was calculated as a function of the chemical potential at various temperatures. These materials are suitable for applications in optoelectronic and thermoelectric devices due to their high thermopower and narrow bandgap. [ABSTRACT FROM AUTHOR]