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This study involves the investigation of the double perovskite A2NbTbO6 (A = Ca, Sr, and Ba) using the PBE-GGA approximation under the quantum-based DFT (density functional theory) within the WIEN2k code. The materials A2NbTbO6 (A = Ca, Sr, and Ba) are cubic crystals with space group Fm3m-225 and non-magnetic behavior. The structural, electrical, optical, and thermoelectric characteristics of the given materials have been investigated. Band gap and density of state calculations are used to explain the electronic properties of the materials under study with the PBE-GGA approximation. The results made it abundantly evident that the materials are pure semiconductors with direct band gaps. Complex dielectric function, refractive index ƞ(ω), extinction coefficient K(ω), optical conductivity σ(ω), absorption coefficient α(ω), reflectivity R(ω), and loss parameter L(ω) are analyzed to explain the optical behavior of the materials. Charge carrier concentration (n), electrical conductivity (σ/t), Seebeck coefficient (S), power factor (PF), thermal conductivity (K/t), specific heat capacity (Cv), and magnetic susceptibility (χ) are investigated to find the material's thermal properties which show the ability of materials in green energy (eco-friendly) production devices and good candidates for optoelectronics especially for solar cell. The BoltzTraP code, which is part of the WIEN2k code, is used to calculate these properties. The cubic compounds Ca2NbTbO6, Sr2NbTbO6, and Ba2NbTbO6 have band gaps of 1.93 eV, 1.89 eV, and 1.87 eV, respectively and are direct band gap materials are confirmed from the band gap structures. By these calculations, all the characteristics are examined to produce new materials for sustainable devices and renewable energy applications like solar cells, and optoelectronics. [ABSTRACT FROM AUTHOR]

Hydrogen storage in the solid state method focuses more on attraction and requires large-scale research. Ab initio calculations of zinc-based Alkali metal hydrides X2ZnH4 (X = K, Rb and Cs) were performed to analyse the structural, electronic, thermal, and elastic properties. Studied hydrides are stable in the orthorhombic phase with space group16- PP222. Phonon dispersion curves are calculated at ambient conditions reveals thermodynamic stability. Electronic band structures and density of states reveal that these hydrides are direct bandgap semiconductors. Also, thermoelectric properties like thermal conductivity, electrical conductivity, specific heat capacity, Seebeck coefficient, Hall coefficient and carrier concentration are investigated using BoltzTraP software. In addition, the elastic constants have been calculated, and the mechanical properties such as bulk modulus, shear modulus, Young's modulus and Poisson's ratio have been calculated using these elastic constants. According to well-known Born stability criteria, K2ZnH4 and Rb2ZnH4 are mechanically stable, while Cs2ZnH4 is unstable. These hydrides might be used in hydrogen storage applications due to moderate gravimetric hydrogen density, which is 2.7 wt%, 1.6 wt%, 1.2 wt% for K2ZnH4, Rb2ZnH4, Cs2ZnH4, respectively. [ABSTRACT FROM AUTHOR]

Structural, electronic, magnetic and elastic characteristics of do half-Heusler alloys CsXB (X = Mg and Sr) are investigated by using First-principles study based on density functional theory. Full-potential linearized augmented plane wave method is used to study these compounds in WIEN2k. The generalized gradient approximation that Perdew–Burke–Ernzerhof developed is used to deal with the exchange correlation function. The elastic characteristics have been employed with the IRelast package, which is already included into WIEN2K. Band structure and density of states are used to describe electronic properties which indicate the half-metallic nature of these compounds. Both CsMgB and CsSrB have minimum energies for spin channel. According to our calculations, CsMgB has a gap of 0.44 eV for spin down channel while CsSrB shows a gap of 0.34 eV for spin up channel. These two compounds exhibit half-metallic characteristic with total integer magnetic moment per formula unit, i.e., 2.00002 for CsMgB and 2.00004 µB of CsSrB which is in well accordance with the Slater–Pauling rule [Mtot = (8−Ztot) µB]. Both compounds are mechanically stable and reveal ductile nature. The obtained results reveal that CsSrB and CsMgB compounds are HM ferromagnets with perfect spin polarization in the absence of transition metals which make them promising candidates for spintronic devices. [ABSTRACT FROM AUTHOR]

Renewable energy prices are decreasing, making it easier to make energy systems that are good for the environment. High-density storage for renewable energy is possible with hydrogen. This work focuses on the theoretical study of LiXH3 (where X = Ti, Mn, and Cu), including their structural, electronic, mechanical, thermoelectric, and hydrogen storage properties, using first-principles calculations. LiCuH3 is more stable than LiMnH3 and LiTiH3, based on the optimization graph. The electronic properties show the metallic nature of these studied hydrides. Born's criterion indicates that all studied hydrides are brittle for various mechanical applications. LiTiH3, LiMnH3, and LiCuH3 are all thought to be able to store hydrogen with gravimetric storage capacities of 5.22%, 4.66%, and 4.11%, respectively. Based on how their thermoelectric properties change with temperature, all the materials under study can absorb heat energy, which shows that they are both electrically and thermally conductive. [ABSTRACT FROM AUTHOR]

Hydrogen storage is attractive in research interests due to clean, renewable and green energy properties of hydrogen. Therefore, frequently research studies are carried out to find suitable and innovative materials that fulfill the criteria of hydrogen storage materials. First-principles calculations of ZrXH3(X = Co , Ni and Cu) compounds are carried out to find their hydrogen storage properties by using CASTEP code. Structural, mechanical, electronic and optical properties of these materials have been studied. Gravimetric hydrogen storage densities of these materials are also calculated. Electronic properties of these hydrides are also discussed which show the metallic nature of these hydrides. Moreover, mechanical properties identified through elastic constants proved their mechanical stability by satisfying Born stability criteria. Bulk, shear, Young's moduli, Poisson's ratio and Vickers hardness show that these three compounds are hard, ductile and have good resistance toward change. We have also calculated the phonon dispersion curves and phonon density of states by using density functional perturbation theory. [ABSTRACT FROM AUTHOR]

Hydrogen can be utilized as an energy source; therefore, hydrogen storage has received the most appealing examination interest in recent years. The investigations of hydrogen storage applications center fundamentally around the examination of hydrogen capacity abilities of recently presented compounds. XSrH3 (X = K and Rb) compounds have been examined by density functional theory (DFT) calculations to uncover their different characteristics, as well as hydrogen capacity properties, for the first time. Studied compounds are optimized in the cubic phase, and optimized lattice constants are obtained as 4.77 and 4.99 Å for KSrH3 and RbSrH3, respectively. These hydrides have shown negative values of formation enthalpies as they are stable thermodynamically. XSrH3 might be used in hydrogen storage applications because of high gravimetric hydrogen storage densities, which are 2.33 and 1.71 wt% for KSrH3 and RbSrH3, respectively. Moreover, electronic properties confirm the semiconductor nature of these compounds having indirect band gaps of values 1.41 and 1.23 eV for KSrH3 and RbSrH3, respectively. In addition, mechanical properties from elastic constants such as Young modulus and Pugh's ratio, also have been investigated, and these compounds were found to satisfy born stability conditions. Furthermore, Pugh's ratio and Cauchy pressure show that these hydrides have a brittle nature. Furthermore, thermodynamic properties such as entropy and Debye temperature have been examined using the quasiharmonic Debye model for different temperatures and pressures. [ABSTRACT FROM AUTHOR]

Cubic perovskites have picked up a potential intrigued by the researchers for their wide-ranging applications within the field of optoelectronic and thermoelectric devices. The research work illustrated in this article mainly emphases on the theoretical study of silicon-based perovskites SiMO3 (M = Sn, Pb) for which density functional theory centered on the first principle technique within the full-potential linearized augmented plane wave method and generalized gradient approximation is utilized within the WIEN2k code. The examined materials are stable in the cubic phase, which is affirmed by its structural properties. The examined results reveal that SiSnO3 and SiPbO3 have indirect bandgap values 0.7 eV and 0.9 eV respectively and showing semiconducting behavior. Also, the optical parameters of the examined compounds have been investigated in expressions of dielectric functions, extinction coefficient, refractive index, reflectivity, absorption coefficient, and energy loss factor. Both materials are sensitive to ultraviolet light in the electromagnetic spectrum perceived by the optical properties. The transparency and maximum reflectivity to the definite energies and the proof of Penn's model indicates that the compounds are more practicable for optical device applications. Lastly, the thermoelectric properties are estimated by elucidating the Boltzmann transport equation. The outcomes of thermal properties tell that SiSnO3 and SiPbO3 have ZT of 0.58 and 0.59, respectively. The p-type conductivity of the studied perovskite materials discloses on the basis of a positive Seebeck coefficient. Both compounds work at their best at 800 K, proposing high-temperature thermoelectric device applications. [ABSTRACT FROM AUTHOR]

At high pressure, the pressure dependencies of the structural, electronic, optical, and thermoelectric properties of Fe 2 HfSi Heusler were calculated using the FP-LAPW method within the framework of the density functional theory. The calculations were carried out using the modified Becke-Johnson (mBJ) scheme. Our calculations showed that the Born mechanical stability criteria confirmed the mechanical stability in the cubic phase. Further, through Poisson and Pugh's ratios critical limits, the findings of the ductile strength were computed. At a pressure of 0 GPa, the indirect nature of the material may be deduced from the electronic band structures of Fe 2 HfSi as well as the estimations for its density of states. Under pressure, the real and imaginary dielectric function responses, optical conductivity, absorption coefficient, energy loss function, refractive index, reflectivity, and extinction coefficient were computed in the 0-12 eV range. Using semi-classical Boltzmann theory, a thermal response is also studied. As the pressure rises, the Seebeck coefficient decreases, while the electrical conductivity rises. The figure of merit ( ZT ) and Seebeck coefficients were determined at temperatures of 300 K, 600 K, 900 K, and 1200 K in order to better understand the thermoelectric properties of a material at these different temperatures. Despite the fact that the ideal Seebeck coefficient for Fe 2 HfSi was discovered at 300 K and was determined to be superior to that reported previously. Materials with a thermoelectric reaction has been shown to be suitable for reusing waste heat in systems. As a result, Fe 2 HfSi functional material may aid in the development of new energy harvesting and optoelectronic technologies., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)