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Effective hydrogen storage is a crucial requirement for harnessing hydrogen as an energy source. Among various storage methods, solid-state hydrogen storage holds promise but necessitates extensive investigation. This study employs density functional theory within the WIEN2k code to improve the desorption temperature and kinetic properties of MgH 2 by introducing Be in combination with transition elements (Ni, Cu, and Zn). The gravimetric hydrogen storage capacity for all studied compounds exceeds 6%. Introduction of different transition elements with Be leads to improvements in formation and cohesive energies, as well as in desorption temperature. Mechanical stability, determined through elastic constants, is confirmed for all hydrides meeting the Born stability criteria. Detailed analyses encompass bonding characteristics, shear modulus, bulk modulus, Cauchy pressures, elastic anisotropy, and Vickers Hardness tests. Electronic properties reveal that Mg 2 BeZnH 8 exhibits the semiconductor nature, and properties are further improved by using TB-mBJ approach. Electronic charge density calculations unveil interatomic bonding nature. Numerous previously unexplored thermodynamic aspects of these hydrides have been investigated and are now presented. • Orthorhombic Mg 2 BeTMH 8 (TM = Ni, Cu and Zn) have been investigated by using density functional theory. • The gravimetric hydrogen storage capacity for all compounds studied exceeds 6%. • Mg 2 BeZnH 8 has low desorption temperature than other two studied hydrides. • All the studied materials are mechanically stable and hard. • Electronic properties reveal that these hydrides exhibit semiconductor nature, except Mg 2 BeNiH 8. [ABSTRACT FROM AUTHOR]

Hydrogen is a promising clean energy source to address the energy issue as well as the environmental and health risks of current energy sources. Metal hydrides have demonstrated significant potential for storing hydrogen. The perovskite hydrides AMgH 3 (A = Be, Ca) have demonstrated potential for hydrogen storage applications due to their impressive gravimetric hydrogen density of 8.32 and 4.49 wt% for BeMgH 3 and CaMgH 3 , respectively. The calculated results indicate that AMgH 3 (A = Be, Ca) perovskite hydrides exhibit metallic character. The AMgH 3 (A = Be, Ca) compounds mostly absorb quanta of energy in the IR range, but they also exhibit high absorption in the UV region. The formation enthalpies of these hydrides have been found to be negative, indicating that they are thermodynamically stable. Furthermore, it has been established that these perovskite hydrides are mechanically stable as they fulfil Born stability criteria. [Display omitted] • Hydrogen storage properties of AMgH 3 (A = Be, Ca) are investigated using DFT approach. • AMgH 3 (A = Be, Ca) show metallic character as their energy bandgap value is 0 eV. • They show remarkable gravimetric H-densities of 8.32 and 4.49 wt%. • AMgH 3 (A = Be, Ca) perovskite hydrides exhibit thermodynamic and mechanical stability. [ABSTRACT FROM AUTHOR]

This figure shows the relationship between formation energy and desorption temperature with pressure. Desorption temperature decreases with increasing pressure, while formation energy increases with increasing pressure value. Due to decreased desorption temperature, MgFeH 3 can be used for hydrogen storage at higher pressures. Still, the problem is that the system moves towards instability at higher pressures. [Display omitted] • Theoretically investigated structural, phonon, thermodynamic and electronic properties of MgFeH 3 at different pressures. • Hydrogen storage properties, along with formation energy and desorption temperature, are also discussed. • Desorption temperature improves while the stability of the system decreases with higher pressures. • Electronic properties indicate the metallic nature of MgFeH 3 at different pressures. • Optical properties of MgFeH 3 are improved with an increase in pressure. The main objective of this work is to improve the kinetic properties and desorption temperature of MgFeH 3 by applying different pressures with the help of the WIEN2k code. We have theoretically determined that MgFeH 3 has a 3.64 wt% gravimetric hydrogen storage capacity. The formation energy and desorption temperature of MgFeH 3 significantly improve with increasing pressures. Phonon dispersion curves predict that the stability of the compound decreases with increasing pressure. Electronic properties show the metallic nature of the studied compound at all pressures. At the same time, DOS shows that d-states of Fe move from the valence to the conduction band with increasing pressures. In thermodynamic properties, we have calculated entropy, specific heat at constant pressure (C p), thermal expansion coefficient (α) as well as Debye temperature (θ D). Optical properties are also calculated for 0–100 GPa pressures in terms of absorption of light energy in visible to ultraviolet regions, refractive index, reflectivity spectrum, and optical conductivity. [ABSTRACT FROM AUTHOR]

The cubic perovskite structures have enlarged the potential for their wide applications for the purpose of hydrogen storage. The present research work aims at undergoing the theoretical study of perovskite type hydrides Li X H 3 (X = Ba, Sr and Cs). The study includes the investigation of structural, electronic and thermal and thermodynamic properties using full potential linearized augmented plane wave (FP-LAPW) method under the frame work of Density Functional Theory (DFT) by employing WIEN2k code. The calculated parameters for structural, electronic and thermal properties are in good agreement with the literature work. Results reveal that all the compounds have indirect band gaps of values of 1.48eV, 1.35eV and 1.73eV for LiBaH 3 , LiCsH 3 and LiSrH 3 , respectively and these calculated band gaps are in good agreement with other theoretical work. In addition, the thermoelectric properties calculated by solving the Boltzmann transport equation reveal that LiBaH 3 possesses superior electrical properties in comparison with the LiSrH 3 and LiCsH 3. Using density functional perturbation theory, we have also calculated the phonon dispersion curves and phonon density of states with the help of the CASTEP code. Various thermo-dynamical properties, such as heat capacity, Debye temperature, Enthalpy, Entropy and free energy have been calculated with the help of thermodynamic functions by using phonon density of states and results reveal that LiBaH 3 is more stable as compared to LiSrH 3. Moreover, results also exhibit that LiCsH 3 is an unstable compound in the cubic phase. • First principle studies of Li X H 3 (X = Ba, Sr and Cs) hydrides. • All the compounds have indirect band gaps. • Various thermo-dynamical properties are investigated. • The studied compounds are suitable for hydrogen storage. [ABSTRACT FROM AUTHOR]

First-principles calculations have been used to study the structural, mechanical, and hydrogen storage properties of the perovskite hydrides, XAlH3 (X = K, Rb, and Cs). The simulated pattern of X-ray diffraction (XRD) also confirmed their polycrystalline structure. The investigation of hydrogen storage properties has led to the determination of gravimetric hydrogen storage capacities for KAlH 3 , RbAlH 3 , and CsAlH 3 , which are found to be 4.38, 2.62, and 1.86 wt%, respectively. Furthermore, the hydrogen desorption temperatures are determined to be 448.43, 507.96, and 487.22K for KAlH 3 , RbAlH 3 , and CsAlH 3 , respectively. The calculation of elastic constants has confirmed that these compounds are mechanically stable. The computed elastic constants have determined the bulk modulus, Young's modulus, shear modulus, and Poisson's ratio. Using ELATE software, 3D visualization of anisotropic elastic properties i.e., maximum and minimum values of Young's modulus, linear compressibility, shear modulus, and Poisson's ratio along with anisotropic factors have been analyzed. Thermodynamic properties involving entropy, Debye temperature, specific heat capacity at constant pressure, and coefficient of thermal expansion have also been calculated. The electronic properties of these compounds confirmed their metallic behavior. These findings provide insight into Al-based perovskite hydrides and their potential applications for hydrogen storage perspectives. [Display omitted] • XAlH 3 (X = K, Rb and Cs) with cubic structure have been investigated using DFT. • XAlH 3 compounds are mechanically stable, and show 3D anisotropic behavior in all elastic properties except linear compressibility. • The hydrogen storage properties and thermodynamic stability make promising materials for hydrogen storage. [ABSTRACT FROM AUTHOR]

A systematic study has been performed on structural, optical and thermophysical properties of newly designed pyrochlore oxides Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) employing FP-LAPW based first-principles calculations. The GGA approach was used to treat exchange and correlation potentials. The investigated E-V plots reveals that Sr 2 Sb 2 O 7 is the most stable structure compared to Be 2 Sb 2 O 7 /Ca 2 Sb 2 O 7. A direct energy bandgap of 0.29 eV is evident from band structure plot of Be 2 Sb 2 O 7 , however, Ca 2 Sb 2 O 7 /Sr 2 Sb 2 O 7 possess indirect energy bandgaps of magnitude 1.47/1.467 eV. The studied materials show maximum absorption of incoming photons in near UV region as shown in ε 2 (ω) plots, however, considerable absorption in visible region is also present. Ca 2 Sb 2 O 7 /Sr 2 Sb 2 O 7 are effective optical material with a n (ω) value between 1.0 and 2.0. Optical properties of pyrochlore oxides reveal that these materials are potential candidates for shielding materials in upper UV region. A photon reflection of up to 60% is evident from the R (ω) in UV region, however, in IR and visible regions, the reflectance is negligible. Based on calculated values of Seebeck coefficient (S), we can state that Be 2 Sb 2 O 7 is n-type semiconductor whereas Ca 2 Sb 2 O 7 /Sr 2 Sb 2 O 7 are p-type semiconductors. The most effective thermoelectric material among Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) is Ca 2 Sb 2 O 7 as its ZT value is highest (∼1.05) in the entire temperature range. Thermodynamic properties of Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) are also evaluated to check dynamical stability and appropriateness of these materials in thermal applications. The investigated outcomes show that these pyrochlore oxides are potential candidates for thermoelectric and optoelectronic device applications. • Ground state properties of pyrochlore oxides Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) are investigated using ab-initio. • Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) are narrow band semiconductors. • Be 2 Sb 2 O 7 is n-type semiconductor, however, Ca 2 Sb 2 O 7 /Sr 2 Sb 2 O 7 are p-type semiconductors. • Optical spectra show major absorption peaks for these pyrochlore oxides occur in visible region. [ABSTRACT FROM AUTHOR]

In this article, the physical properties of XCrS 2 (X = Zn, Cd, and Hg) are studied by Density Functional Theory (DFT) using Wien2K code. Stability, along with certain parameters of the crystal structures of the compounds, was evaluated based on PBE-GGA. Mechanical properties reveal that the studied compounds XCrS 2 (X = Zn, Cd) are stable, and their elastic constants and Paugh's ratio exhibit that ZnCrS 2 is brittle, whereas CdCrS 2 is ductile in nature. Furthermore, HgCrS 2 does not satisfy the Born stability criteria. The modified Becke-Johnson (mBJ) potential was used to improve the band gap properties and results depict that the XCrS 2 (X = Zn, Cd) compounds have 1.30 and 1.27 eV direct band gaps, respectively. Thermoelectric properties exhibit the highest optical conductivity with energy loss and the strongest absorption is observed for CdCrS 2 in the visible region, which also has the best photovoltaic activity. The higher obsorption nature makes this material a good candidate for solar devices. The electrical and thermal conductivity increase with an increase in temperature, and ZnCrS 2 has a greater ZT compared to CdCrS 2. [ABSTRACT FROM AUTHOR]

The optoelectronic, structural, and transport properties of the ternary chalcogenides Na 2 GeX 3 (X = S, Se Te) are investigated by the full-potential linearized augmented plane wave (FP-LAPW) method. Na 2 GeS 3 and Na 2 GeSe 3 have a direct bandgap, while Na 2 GeTe 3 is an indirect bandgap material. The magnitude of the bandgap decreases by replacing S with Se and Te. Optical parameters such as dielectric function, refractive index, reflectivity, absorption coefficient, and energy loss function are also calculated to check their potential in optoelectronic applications. The considered chalcogenide compounds may be promising candidates for photovoltaic devices operating in the UV regions due to their high absorption coefficient in these regions. The calculated thermoelectric parameters (electrical and thermal conductivity, Seebeck coefficient, figure of merit, power factor) indicate that the Na 2 GeX 3 chalcogenides are promising for potential applications in thermoelectric devices. • Electronic, optical and thermoelectric properties of Na 2 GeX 3 (X = S, Se, Te) are investigated ab-initio. • Na 2 GeS 3 and Na 2 GeSe 3 are direct bandgap semiconductors while Na 2 GeTe 3 has an indirect bandgap. • Optical spectra show a major absorption peak between 2.0–9.0 eV. • Among the considered compounds, Na 2 GeTe 3 shows the highest absorption. • Na 2 GeX 3 are potential candidates for applications in optoelectronic and thermoelectric devices. [ABSTRACT FROM AUTHOR]

Based on ab-initio calculations in the framework of the density functional theory (DFT), an analysis of the structural, magnetic, thermoelectric, and optoelectronic properties of three newly designed ternary semiconductor sulfides: LaTlS 2 (La = Er, Eu, Tb) is carried out. It has been established that these compounds are thermodynamically and mechanically stable. Indirect bandgaps are found with the values 1.53, 1.62, 1.70 eV for the spin up (↑) channel for ErTlS 2, EuTlS 2, TbTlS 2, respectively. For the spin down (↓) channel, the obtained values are slightly lower. The paramagnetic magnetic moments are predicted by observing different band shapes in the energy band structures for the spin up (↑) and spin down (↓) states. The values of the magnetic moments for ErTlS 2 , EuTlS 2 and TbTlS 2 are large, being respectively: 3.00, 6.00 and 6.00 μ B. The R (ω) spectra show a very low reflectance in the IR and visible regions, however, up to 45% of the photon reflection occurs in the UV region. The spectra of the Seebeck coefficient show that EuTlS 2 is initially p-type semiconductor, but becomes n-type semiconductor above 350 K. Whereas ErTlS 2 and TbTlS 2 are initially n-type semiconductors, but become p-type semiconductors at temperatures higher than 100 K. [ABSTRACT FROM AUTHOR]

Based on density functional theory (DFT), we present the structural, electronic, magnetic and half-metallic properties of M x Sc 1-x P (M = Cu, Zn; x = 0.125, 0.25, 0.375) by using the full potential linearized augmented plane wave (FP-LAPW) method. ScP in zinc blende structure in the undoped state exhibits semiconducting properties. To investigate the changes in electronic and magnetic properties, supercells created used different parameters and dimensions are doped with 3d10 based transition metal impurities. By doping the impurities Cu and Zn in different concentrations, half-metallic ferromagnetic properties are observed in Cu 0.125 Sc 0.875 P and Zn 0.125 Sc 0.875 P. At reduced volume, Cu 0.25 Sc 0.75 P and Zn 0.25 Sc 0.75 P also exhibit half-metallic properties in the ferromagnetic phase. The GGA + U method also confirms the half-metallic behavior of these compounds. The ternary MScP and quaternary MSc 2 P (M = Cu, Zn) are observed to be stable in the non-magnetic phases and exhibit metallic properties. M x Sc 1-x P (M = Cu, Zn; x = 0.125, 0.25) have negative cohesive energies, 100% of spin polarization at the E F , magnetic moments of integer values and exhibit half-metallic properties, thus providing a platform to the experimentalists in synthesizing them for spintronics technology. • ScP in zb phase exhibits semi-conducting properties. • Cu and Zn in 12.5%, 25% and 37.5% concentration are doped in the supercell Sc 8 P 8. • Cu 0.125 Sc 0.875 P and Zn 0.125 Sc 0.875 P exhibit half-metallic ferromagnetism. • At reduced volume Cu 0.25 Sc 0.75 P and Zn 0.25 Sc 0.75 P show a transition from AFM to Ferromagnetic phase. • ScP doped with Cu has larger magnetic moments than ScP doped with Zn. [ABSTRACT FROM AUTHOR]