Hydrogen is a promising candidate for green energy sources for future endeavors because of its abundance on Earth. Although its storage is a major challenge for the researchers of this era because of its unsafe and highly explosive nature. The structural, optoelectronic, thermoelectric, vibrational, thermodynamic properties and hydrogen storage capacity of XMgH 3 ([Formula: see text], Ba) are carried out by using the full potential linearized augmented plane wave (FP-LAPW) method in the DFT framework. The theoretical study about these magnesium-based metal hydride perovskites, i.e., SrMgH 3 and BaMgH 3 , declares them structurally stable compounds in space group Pm-3m. The optimization graph for SrMgH 3 and BaMgH 3 reflects the lowest ground state energy, i.e., −6759[Formula: see text]Ry and −16683[Formula: see text]Ry, respectively. Comparatively, BaMgH 3 seems to be more stable. The electronic band structures and density of states declare them pure metallic due to zero band gap and overlapping of electronic states of the valence and the conduction bands. The electrical conductivity of BaMgH3 increases up to [Formula: see text] and thermal conductivity [Formula: see text] in the temperature range 100[Formula: see text]K to 1000[Formula: see text]K revealing the good metallic character of BaMgH 3 . The optical analysis portrays the absorption of compounds in the visible range along with valance shell electrons to the weak bond of hydrogen and dissociates hydrogen molecules at a certain intensity of light. BaMgH 3 compound shows minimum scattering and maximum absorption of light in the visible region up to 3[Formula: see text]eV. The reflectivity peaks in the visible region 3.0[Formula: see text]eV show that 40% of light energy is absorbed due to the opaque nature of BaMgH 3 . Both these compounds are declared thermodynamically stable due to negative free energy such as −1.20[Formula: see text]eV for SrMgH 3 and −1.50[Formula: see text]eV energy for BaMgH 3 at 1000[Formula: see text]K, respectively. Moreover, the three acoustic modes showing zero imaginary phonon frequencies at [Formula: see text] symmetry points predict these compounds’ structural and thermodynamical stability. The gravimetric hydrogen storage concentration of SrMgH 3 and BaMgH 3 is determined as 2.637% and 1.836%, respectively.

In this study CoZrMnSb, a quaternary Heusler alloy has been explored utilizing the density functional theory based simulation package WIEN2k. The structural analysis exhibits an X1-type structure with a relaxed lattice constant of 6.27 Å in ferromagnetic phase. The band structure calculations show its half-metallic nature with full spin polarization states around the Fermi level at 0.56 eV energy. In addition, the magnetic moment is calculated to be 1.0 μB, which is in accordance with the Slater Pauling rule (Mtot = (Ztot–24) μB). The study shows the d-d hybridization of the transition metals Co, Zr, and Mn elements. Further, optoelectronic performances in terms of dielectric function, reflectivity, energy loss function, absorption coefficient have been determined for a range of photon energy up to12 eV (ultraviolet region). In optoelectronic applications, absorption of this material in visible light enhances its significance. The thermoelectric properties with chemical potential and thermodynamic properties in the pressure range of 0–40 GPa and temperature range of 0–1200 K have been analysed. Specific heat capacity and Debye temperature authenticate similar metallic behaviour of CoZrMnSb alloy at temperature versus pressure variations. At room temperature, the chemical potential study suggests high figure of merit 0.9, which makes it a potential thermoelectric material. The suggested material has a high Seebeck coefficient and low thermal conductivity, making it a better match for waste heat recovery and spintronic applications.

Storage of hydrogen is a necessary prerequisite for the commercialisation of hydrogen used in the production of energy. The solid-state storage of hydrogen is one of the many different methods for storing hydrogen, requiring much research. This work aims to optimise the desorption temperature and kinetic characteristics of MgH2 by introducing Be doping at varying concentrations using density functional theory within the WIEN2k code. Gravimetric hydrogen storage capacity increases as the Be concentration increases. Formation energy, cohesive energy and desorption temperature improve with the doping of Be. Elastic constants are then used to determine which hydrides are mechanically stable. All of the hydrides, except for MgBe3H8, meet the Born stability conditions, which means that they are mechanically stable. The bonding characteristics, shear modulus, bulk modulus, Cauchy pressures and Vicker's hardness test are all measured and analysed. These hydrides can be classified as semiconductors based on their electronic properties, and bandgap values decrease with the concentration of Be. Many previously undiscovered thermodynamic features of these hydrides are examined and presented. The Seebeck coefficient, a figure of merit, and electrical and electronic-thermal conductivities are also calculated to investigate the thermoelectric properties.

At high pressure, the pressure dependencies of the structural, electronic, optical, and thermoelectric properties of Fe2HfSi 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 Fe2HfSi 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 Fe2HfSi 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, Fe2HfSi functional material may aid in the development of new energy harvesting and optoelectronic technologies.