Calculated Lattice Parameters Research Articles

Structural, magnetic and magnetocaloric properties of TMCeFeO4 (TM = Mn, Co) spinel ferrites powders

In this paper, a successfully synthesized TMCeFeO4 (TM = Mn, Co) by the sol–gel technique has been studied in detail. The structural, magnetic and magnetocaloric properties are performed using an X-ray powder diffractometer and a vibrating sample magnetometer (VSM). X-ray diffraction (XRD) analysis shows that both samples belong to the Fd-3m space group of the cubic spinel crystal system. Moreover, the calculated lattice parameters of MnCeFeO4 and CoCeFeO4 samples are found to be 8.409Å and 8.397Å, respectively. On the other hand, temperature and field dependent magnetization curves demonstrate that both samples exhibit a second-order ferromagnetic (FM)-paramagnetic (PM) phase transition at TC=640K and 630K for MnCeFeO4 and CoCeFeO4, respectively. The maximum of magnetic entropy change -ΔSMmax, calculated from Maxwell relation at an applied magnetic field change of μ0ΔH=5T, are found to be 0.404 and 0.463JKg-1K-1 corresponding to relative cooling powers (RCPs) about 41.62 and 41.53JKg-1 for MnCeFeO4 and CoCeFeO4, respectively.

Rapid response in recovery time, humidity sensing behavior and magnetic properties of rare earth(Dy & Ho) doped Mn–Zn ceramics

In the present world, the development of room temperature humidity sensor materials has always been a very popular research field. Rare earth (RE) doped ferrites are considered as potential resistive humidity sensing material owing to its high remarkable surface morphology with high porosity. Recent studies have shown that ferrite ceramics have good response in recovery time and have excellent humidity sensing behavior. With this in mind, solution combustion synthesis was used to effectively prepare RE dysprosium (Dy3+) and holmium (Ho3+) doped Mn–Zn ferrite ceramics with the chemical formula Mn0·5Zn0.5DyxHoyFe2-xO4 (x = 0.005 to 0.03) (MZDHF) (where x, y = 0.0, 0.01, 0.015, 0.02, 0.025 and 0.03). The MZDHF XRD pattern revealed the purity of the samples without any secondary phase. The crystallite size MZDHF is in the nano range. Further, the calculated lattice parameter of MZDHF is found to be increasing with the RE content. The two prominent major absorption bands related to A-site and B-site were confirmed by FTIR spectra. The hysteresis loops of MZDHF are used to investigate the differences in magnetic properties with an Dy3+-Ho3+ concentration. The remanence magnetization, saturation magnetization, coercivity and anisotropy of the ferrites were determined. The saturation magnetization decreases with increase of Dy3+-Ho3+ concentration. The change in the surface resistance for all the samples was studied. Among all the samples, Mn0·5Zn0.5Dy0.03Ho0.03Fe1·96O4 composite has shown a drastic variation in resistance. And the corresponding sensing response for the same sample is found to be 99%. Along with this, the sample has shown a least hysteresis and good stability. Also, the Mn0·5Zn0.5Dy0.03Ho0.03Fe1·96O4 composite has shown a good timing behavior of 90 s and 18 s. The sensing mechanism for the prepared Mn0·5Zn0.5Dy0.03Ho0.03Fe1·96O4 composite was thoroughly discussed.

Growth of spherical carbon nitride with crystalline alpha and beta phases

Carbon is a versatile element, and its allotropes play a center role in both science and technology. Further, doping of nitrogen into carbon network has been of great interest as it leads to superior properties such as chemical, mechanical and electronic properties. Though the preparation of ultrahard β-carbon nitride remains challenging one, it owes great attention due to its superior properties. This work reports preparation and characterization of crystalline carbon nitride on silicon (100) substrate. The X-Ray diffraction revealed that the deposited film- have α and β carbon nitride crystalline phases. The calculated lattice parameters are found to be a = 6.26 Å, c = 2.38 Å for β-C3N4 and a = 6.8 Å, c = 4.6 Å for α-C3N4. The X-Ray photoelectron spectroscopy study confirms that carbon atom is bonded tetrahedrally (sp3) with nitrogen atoms as expected for the formation of crystalline C3N4, and also the presence of C = N trigonal (sp2) bond. The surface morphology of the film examined by field emission scanning electron microscopy shows the formation of carbon nitride spheres.

Effect of dopants on the structural, optoelectronic and magnetic properties of pristine AgGaO3 perovskite: A first principles study

The structural, electronic and optical properties of pristine AgGaO3 and doped Ag1-xCrxGaO3 (x = 0.25, 0.50 and 0.75 at%) have been explored using first principle simulation based on density functional theory (DFT). The Perdew-Burke-Ernzerhof – Generalized Gradient Approximation (PBE-GGA) is used to optimize the geometry of pristine and Cr doped AgGaO3 systems. Structural analysis demonstrates that the calculated lattice parameters and unit cell volume decrease with the increase of Cr concentration. The incorporation of Cr at Ag sites significantly affects the electronic band gap of AgGaO3. All materials are found to be semiconductor with direct band gap values of 1.42 eV, 1.26 eV, 0.65 eV and 0.37 eV for pristine AgGaO3 and Cr doped Ag1−xCrxGaO3 (at x = 0.25, 0.50, 0.75 at%), respectively. The localized energy states of 75% Cr doped AgGaO3 play significant role to enhance optical conductivity. Further, Penn’s model is confirmed by observing the inverse relationship between the dielectric function and electronic band gap. The significant variations noted in electronic band gap as well as optical characteristics caused by the doping of Cr declares that the doped materials are more appropriate candidates for solar cell and optoelectronic like applications as compared to pristine AgGaO3. It is further established that magnetism is induced in all Cr doped perovskites. The net magnetic moment computed for each Cr atom is 3 μB. All doped systems are found to be ferromagnetic in nature.

PECULIARITIES OF SINGLE CRYSTAL GROWTH OF SOLID SOLUTION IN SYSTEMS Ag6PS5I‒Ag7GeS5I AND Ag7SiS5I‒Ag7GeS5I

The application of innovative resolutions that are technically grounded and economically acceptable with the use of environmentally friendly components is one of the important points at the present stage of human development to promote the ideas of efficient use of energy resources. Superionic conductors take a leading role in solving the problems of energy-saving technologies because electrochemical sensors and solid energy sources based on them can be created. Quaternary silver-containing compounds of argyrodite structure Ag6PS5I, Ag7SiS5I, and Ag7GeS5I have many advantages, in particular chemical stability, high values of ionic conductivity, the ability to form wide series of solid solutions due to the structural features. This work is devoted to the development and optimization of technology for obtaining high-quality single-crystal samples of solid solutions based on compounds of argyrodite structure formed in systems Ag6PS5I‒Ag7GeS5I та Ag7SiS5I‒Ag7GeS5I.
 The synthesis of solid solutions of the investigated systems was carried out by a direct single-temperature method from previously obtained quaternary compounds Ag6PS5I, Ag7SiS5I, and Ag7GeS5I. The maximal temperature of synthesis was 1273 K (exposure 72 h). Cooling to the experimentally selected annealing temperatures of 733 K (Ag6PS5I‒Ag7GeS5I) and 873 K (Ag7SiS5I‒Ag7GeS5I) was performed at a rate of 100 K/h. The annealing was performed for 120 hours.
 Crystal growth of solid solutions based on Ag6PS5I, Ag7SiS5I, and Ag7GeS5I phases was carried out by the directional crystallization from solution-melt by the Bridgman technique. The growth of single crystals was carried out in a three-zone furnace in a quartz container with a conical bottom. The optimal technological regimes for crystal growth of solid solutions of Ag6PS5I‒Ag7GeS5I and Ag7SiS5I‒Ag7GeS5I systems have been established. Grown single crystals of solid solutions Ag6+x(P1-xGex)S5I (х=0.25, 0.5, 0.75) and Ag7(Si1-xGex)S5I (х=0.2, 0.4, 0.6, 0.8) were dark gray color with metallic luster 30-40 mm long and 10-12 mm in diameter. Obtained crystals were investigated by X-ray diffraction analysis. Calculated lattice parameters change according to Vegard’s rule and confirm the formation of solid solutions in studied systems.

Structural, elastic and thermodynamic properties of YRh: DFT study

In the present study, we have performed ab-initio calculations for the equation of state parameters, elastic constants, and thermal properties of (B2-type) Yttrium-Rhodium (YRh) rare earth intermetallic compound. We have employed the projected augmented wave (PAW) pseudopotentials approach in the framework of the density functional theory (DFT) as implemented in the Quantum Espresso code, using both the local density approximation (LDA) and the generalized gradient approximation (GGA). The calculated lattice parameter of YRh compound agree very well with the available experimental one. The obtained results of the elastic constants are in general in good agreement compared to the theoretical ones reported previously in literature. The evaluated mechanical stability criteria indicate that YRh intermetallic compound is mechanically stable at equilibrium, while the anisotropy factor indicates that this material is characterized by a weak degree of anisotropy in its elastic properties. Calculations of Poisson’s ratio (ν) and Pugh’s ratio (B/G) both indicate that YRh intermetallic compound in B2 structure is ductile. Furthermore, several thermodynamic properties of YRh compound have been studied using Quasi-harmonic approximations (QHA). Our Calculations show that the vibrational free energy, the isothermal bulk modulus and the adiabatic bulk modulus decrease with increasing temperature, while all other calculated quantities increase with increasing temperature.

Thermal properties of energetic materials from quasi-harmonic first-principles calculations

The structure and properties at a finite temperature are critical to understand the temperature effects on energetic materials (EMs). Combining dispersion-corrected density functional theory with quasi-harmonic approximation, the thermodynamic properties for several representative EMs, including nitromethane, PETN, HMX, and TATB, are calculated. The inclusion of zero-point energy and temperature effect could significantly improve the accuracy of lattice parameters at ambient condition; the deviations of calculated cell volumes and experimental values at room temperature are within 0.62%. The calculated lattice parameters and thermal expansion coefficients with increasing temperature show strong anisotropy. In particular, the expansion rate (2.61%) of inter-layer direction of TATB is higher than intra-layer direction and other EMs. Furthermore, the calculated heat capacities could reproduce the experimental trends and enrich the thermodynamic data set at finite temperatures. The predicted isothermal and adiabatic bulk moduli could reflect the softening behavior of EMs. These results would fundamentally provide a deep understanding and serve as a reference for the experimental measurement of the thermodynamic parameters of EMs.

Probing the mechanical properties of ordered and disordered Pt-Ir alloys by first-principles calculations

Platinum-iridium (Pt-Ir) alloys are promising superalloys and widely used as bond coating in aero-engines due to its high melting point, outstanding oxidation resistance and excellent corrosion resistance. As solid solution alloy, the mechanical properties of disordered Pt-Ir alloys are calculated with the special quasirandom structures and virtual crystal approximation methods based on density functional theory. Phonon spectrum shows that the ordered and disordered Pt-Ir alloys are all dynamically stable phases. The calculated lattice parameters, elastic constants and modulus of Pt-Ir alloys are in good agreement with the experimental values. The results show that the bulk modulus, shear modulus, Young's modulus are increasing with the increase of Ir content, while B/G and Poisson's ratio decrease. Moreover, the model of the elastic properties is built based on the CALPHAD approach as a function of chemical composition. The electronic basic of mechanical properties are probed by electronic density and weighted mean bond population.

Structural, elastic, vibrational, electronic and optical properties of SmFeO3 using density functional theory

We perform first principles simulations for the structural, elastic, vibrational, electronic and optical properties of orthorhombic samarium orthoferrite SmFeO3 within the framework of density functional theory. A number of different density functionals, such as local density approximation, generalized gradient approximation, Hubbard interaction modified functional, modified Becke-Johnson approximation and Heyd–Scuseria–Ernzerhof hybrid functional have been used to model the exact electron exchange-correlation. We estimate the energy of the ground state for different magnetic configurations of SmFeO3. Its crystal structure is characterized in terms of calculated lattice parameters, atomic positions, relevant ionic radii, bond lengths, bond angles and compared with experimental values. The stability of its orthorhombic structure is simulated in terms of elastic properties. The vibrational phonon modes are calculated using density functional perturbation theory and are shown to be consistent with recent experimental observations. In case of electronic properties, we provide estimates based on density functionals with varying degrees of computational complexities in the Jacob's ladder. We show Heyd–Scuseria–Ernzerhof density functional theory provides better modelling for localized d and f orbitals in SFO which is in line with theoretical work on other rare-earth materials. The linear optical properties in terms of complex dielectric function and other standard optical functions are derived for Hubbard corrected generalized gradient approximation in combination with Fermi's golden rule.These provide a good theoretical analysis of structural, elastic, vibrational, electronic and optical properties of SFO.

First-principles calculations of effects of pressure on paramagnetic, ferromagnetic, and antiferromagnetic spin-web Cu3TeO6.

The structure, electronic, and magnetic properties have been investigated by the first-principles calculations for paramagnetic, ferromagnetic, and antiferromagnetic Cu3TeO6 under pressure from 0 to 100GPa. The calculated lattice parameters at 0GPa are in excellent agreement with the available calculated and experimental values. With increasing pressure, the lattice parameters and volume decrease, but Cu3TeO6 keeps a stable cubic structure. The electronic calculations show that paramagnetic and ferromagnetic Cu3TeO6 are metallic, and antiferromagnetic Cu3TeO6 is non-metallic with a direct band gap which decreases with the increasing pressure. Under the pressure, their non-locality of density of states enhances and the electrons become more active. Moreover, for antiferromagnetic Cu3TeO6, the spin moments of Cu atoms are affected obviously by pressures, and Te atoms show nonmagnetic performance. The total magnetic moment, which is mainly contributed by Cu, reaches the maximum at 20GPa, and decreases with the increasing pressure. The knowledge of these properties will provide reference and guidance for the subsequent study of Cu3TeO6.

First-principles calculations to investigate mechanical, optoelectronic and thermoelectric properties of half-Heusler p-type semiconductor BaAgP

We have explored the mechanical, electronic, optical and thermoelectric properties of p-type half-Heusler compound BaAgP for the first time using density functional theory based calculations. Our calculated lattice parameters are in good agreement with the experimental values. The mechanical and dynamical stability of this compound is confirmed by studying the Born stability criteria and phonon dispersion curve, respectively. It is soft, brittle and elastically anisotropic. The atomic bonding along a-axis is stronger than that along c-axis. The calculated electronic structure reveals that the studied compound is an indirect band gap semiconductor. The analysis of charge density distribution map and Mulliken population reveals that the bonding in BaAgP is a mixture of covalent and ionic. The optical features confirm that BaAgP is optically anisotropic. The high absorption coefficient and low reflectivity in the visible to ultraviolet region make this compound a possible candidate for solar cell and optoelectronic device applications. The thermoelectric properties have been evaluated by solving the Boltzmann semi-classical transport equations. The anisotropic power factor similar to SnSe is found in BaAgP also. The calculated power factor of 2.16 mW/mK2 at 700 K along a-axis is close to that of NbFeSb alloys, a promising half-Heusler thermoelectric material. The thermoelectric figure of merit, ZT (0.44) of BaAgP at 1000 K is low due to its high thermal conductivity. So the reduction of thermal conductivity is essential to enhance thermoelectric performance of BaAgP in device applications.

Y3+ composition and particle size influenced magnetic and dielectric properties of nanocrystalline Ni0.5Cu0.5YxFe2-xO4 ferrites

The rare earth Yttrium (Y3+) doped Ni–Cu nanoferrites (NCY ferrites) with chemical formulation, Ni0.5Cu0.5YxFe2-xO4 (x = 0–0.125) were prepared successfully by the sol gel route. The X-ray diffraction (XRD) of NCY ferrites revealed that a single phase of cubic spinel is created within the synthesized ferrites. The crystallite sizes obtained by XRD pattern are in the range of 51–84 nm, in good agreement with those obtained by transmission electron microscopy (TEM) and field emission scanning electron microscopy (FSEM). The calculated lattice parameter of NCY ferrite unit cells initially decreases up to x = 0.1 and increase afterwards for x = 0.125. From FESEM and TEM micrographs, surface morphology and microstructure of NCY nanoferrites were studied. The energy dispersive X-ray spectroscopy (EDS) patterns have confirmed the stoichiometric presence of Ni, Cu, Y, O and Fe, those were used to prepare the samples. The variations in the magnetic properties with Y3+ compositions were investigated by obtaining the hysteresis loops of NCY ferrites. The magnetic hopping lengths LA and LB were calculated from XRD. The saturation magnetization, Bohr magneton number, coercivity and retentivity of the ferrites were influenced by the structural parameters like crystallite size and lattice strain. The frequency variation of dielectric constant and loss tangent exhibit space charge polarization as a phenomenon governing the dielectric behavior of the ferrites.

Ab initio and Monte Carlo studies of physical properties of semiconductor radiation detectors

The structural and electronic properties of Cd1−xZnxTe and Cd1–xMnxTe compound semiconductors are investigated by using the first-principles pseudopotential plane-wave method based on the density functional theory (DFT). The generalized gradient approximation (GGA) and the local density approximation (LDA) are used. The calculated lattice parameters, the bulk modulus and the electronic band structures of different alloys are found to be in good agreement with the literature data. Absolute, photopeak and intrinsic detection efficiencies, in the 511–1332.5 keV gamma-ray energy range, are investigated using a stochastic approach, which is the Monte Carlo method as implemented in the Geant4 code. The calculated parameters are analyzed in the light of the available data.

A Novel Open-System Method for Synthesizing Muscovite from a Biotite-Rich Coal Tailing

According to the wide application of muscovite in various industries, many studies have focused on its fabrication. However, the process of its synthesis faces long-standing challenges mainly related to the elevated temperature and pressure ambient, together with time and cost-consuming processes. This research work aims at synthesizing muscovite through a straightforward and direct wet thermal oxidation of an ash sample produced from biotite-rich coal tailings. For this purpose, the lab ash powder was mixed with 35% H2O2 at the room temperature of 25 °C while stirring at 480 rpm. Then, the temperature was gradually raised to 80 °C, and the process ran for 180 min. The dried product and the raw lab ash were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) methods. The XRD results indicated that the biotite was efficiently converted to the muscovite as the number of relevant peaks was significantly increased in the synthesized product’s pattern. The SEM and FTIR results showed some structural changes, from pseudo-hexagonal in the starting material to amorphous pseudo-crystals in the synthetic product, as well as the growth of the product’s crystals. The crystallographic study and lattice parameter calculations revealed that the starting material and product peaks matched to International Center for Diffraction Data (ICDD reference patterns of 01-080-1110 and 01-082-2450 for the biotite and the muscovite, respectively. Moreover, the calculation of the mean crystallite size of the starting material and treated samples were obtained as 55 nm and 87 nm, respectively. Finally, according to the characterization properties of synthesized muscovite, the presented method was introduced as an effective technique. Therefore, we highly suggest it for further consideration and its development in future investigations.

Stability, electronic structure, mechanical properties and lattice thermal conductivity of FeS and FeS2 polymorphs

First-principles calculations were used to investigate the stability, electronic structure, elastic and lattice thermal conductivity of FeS and FeS2 polymorphs ([Formula: see text]-FeS, [Formula: see text]-FeS, [Formula: see text]-FeS, [Formula: see text]-FeS2, [Formula: see text]-FeS2). The calculated lattice parameters were in agreement with experimental results. The results showed that these Fe-S binary compounds are thermodynamically and mechanically stable. The elastic anisotropies of Fe-S binary compounds were exhibited by 3D modulus ball and 2D projections. Among all the five compounds, [Formula: see text]-FeS2 compound has the largest bulk modulus and [Formula: see text]-FeS2 has the largest Young’s modulus and hardness. Furthermore, [Formula: see text]-FeS, [Formula: see text]-FeS and [Formula: see text]-FeS compounds can be regarded as ductile material according to [Formula: see text] and Poisson’s ratio. The FeS compounds show metallic character and FeS2 compounds show semiconductor character through analyzing their bandgap and density of states (DOS). The [Formula: see text]-FeS2 has the largest thermal conductivity according to the Clarke model, and the [Formula: see text]-FeS shows the strongest thermal conductivity anisotropy among the five compounds.

Bifacial DSSC fabricated using low-temperature processed 3D flower like MoS2 - high conducting carbon composite counter electrodes

3D flower-like MoS2 nanostructures are synthesised using hydrothermal method at different S:Mo ratios. The grown MoS2 nanostructures exhibit 2H-MoS2 phase with P63/mmc space group, which can be inferred from XRD results. The calculated lattice parameters and inter planar spacing values are in good agreement with the literature. FESEM images show flower like morphology of the grown nanostructures. HRTEM micrographs are used to examine microstructural properties and to determine the interplanar spacing (d). The peaks observed in Raman spectra at ∼380 and ∼404 cm−1 are designated to E2 g1 mode and A1g mode respectively. Elemental analysis is carried out using XPS analysis. Counter electrodes (CE) for dye sensitised solar cells (DSSC) are fabricated using MoS2-high conductive carbon paste (HCP) composite. Simple spin coating method is used to deposit CE with a low annealing temperature of 80 °C which is suitable for even plastic substrates. Using Nyquist and Bode plot, series resistance (9.02 Ω cm2), charge transfer resistance (17.48 Ω cm2) and electron lifetime (63 ms) is calculated. The fabricated DSSC shows a power conversion efficiency of 4.50 % when illuminated from the front side whereas 2.40 % in the case of rear illumination.

A Theoretical Investigation on the Physical Properties of SrPd2Sb2 Superconductor

The high temperature phase of SrPd2Sb2 polymorphs exhibits bulk superconductivity below 0.6 K. The electron phonon coupling constant and density of states are two major factors that control the superconductivity in this intermetallic compound. Here we report the detailed physical properties including structural, elastic, electronic, and optical properties of this superconducting phase by using DFT-based computational method. The calculated lattice parameters and density of states show good agreement with the experimental data. This intermetallic is ductile and comparatively soft with respect to other members of this family. This compound exhibits metallic conductivity mostly emerging from Pd and Sb atoms that is different from other similar type of superconducting materials. The strong covalent interactions in Sb-Sb and Sb-Pd bonds define the electronic characteristics of this superconducting material. The optical properties of this superconductor are fairly comparable with other similar compounds in this family.

Prediction of Lattice Constants of some Transition Metal Nitrides using Different Functionals and Pseudo-potentials

Properties of materials are best analyzed when lattice parameters of such compounds of materials are predicted accurately. In density functional theory prediction of lattice parameters, density functionals play important role in obtaining accurate values. In this study, density functional theory was used to investigate accurate prediction of lattice parameters of some transition metal nitrides. Local Density Approximation (LDA) and Generalized Gradient Approximation of Perdew-Burke-Ernzerhof revised for solids (GGA-PBEsol) functionals combined with ultrasoft and projector augmented wave (PAW) pseudo-potentials were used for the investigation. The results indicated that GGA-PBEsol functional with PAW pseudo-potential performed better in predicting lattice parameters of these compounds. ForFeN compound, the calculated lattice parameter with GGA-PBEsol functional and PAW pseudo-potential was 4.232 Å compared with the experimental values of 4.307 Å and 4.296 Å corresponding to a little underestimation of about 1.74% and 1.49% respectively. Ultrasoft pseudo-potential of GGA-PBEsol functional and LDA functional with the two pseudo-potentials overestimated the lattice parameters for over 5%. It was concluded that, for the functionals and pseudo-potentials considered, GGA-PBEsol with PAW pseudo-potential may be a very good choice for prediction of lattice parameters of binary compounds with transition metals.

DFT based first principles study of novel combinations of perovskite-type hydrides XGaH3 (X = Rb, Cs, Fr) for hydrogen storage applications

Hydrogen storage has become a challenge for researchers of this era because it is a cheap, clean, and non-pollutant element existing in nature. The current study has been performed in order to calculate the structural, electronic, optical, and magnetic properties of perovskite hydrides XGaH3 (X = Rb, Cs, Fr) through the Cambridge serial total energy package code based on density functional theory. The comprehensive investigations have been made while utilizing three cations (Rb, Cs, and Fr) in the cubic form of the ABH3 symmetry phase. The electronic properties of the considered hydrides have been investigated to determine bandgap, total density of states, and partial density of states, and their trends are devised against frequency (eV) of incident radiations. XGaH3 hydrides have shown metallic behavior because no energy bandgap is noticed near the Fermi level. The lattice constants of RbGaH3, CsGaH3, and FrGaH3 by utilizing the Perdew–Burke–Ernzerhof-Generalized Gradient Approximation (PBE + GGA) functional are found to be 4.0754 Å, 4.2137 Å, and 3.1237 Å. The local density approximation functional has also been used for calculations of lattice parameters, which are observed to be 3.9287 Å, 4.0673 Å, and 3.9818 Å, respectively. Anti-ferromagnetism is observed through magnetic analysis of the studied hydrides XGaH3 (X = Rb, Cs, Fr). Regarding the optical analysis, FrGaH3 is found to be a more suitable material for hydrogen storage. These novel materials exhibit minimum energy loss with maximum conductivity. The gravimetric ratio for hydrogen storage capacity is determined to be 2.5 wt. %, 2.0 wt. %, and 2.1 wt. % for RbGaH3, CsGaH3, and FrGaH3, respectively. The present computational calculations of these hydrides are attempted for the first time, which may provide exceptional improvements for applications in hydrogen storage.

Structural, electronic and magnetic properties of Mott insulating Y1-xLaxTiO3 from hybrid density functional calculations

The ferromagnetic (FM)-antiferromagnetic (AFM) transition is experimentally observed in Y1-xLaxTiO3. The underlying microscopic mechanism for FM-AFM transition is still an open problem and far from fully understood. Here, structural, electronic and magnetic properties of Mott insulating Y1-xLaxTiO3 with x = 0, 0.25, 0.5, 0.75, and 1 are studied using hybrid density functional method. Y1-xLaxTiO3 stabilizes in an orthogonal perovskite structure. As x increases, the lattice parameters and unit volume almost increase linearly. Y1-xLaxTiO3 is an FM insulator at x = 0 and 0.25, an A-type AFM insulator at x = 0.5 and 0.75, and a G-type AFM insulator at x = 1. A spin-glass behavior is predicted to emerge at 0.25 < x ≤ 0.5. The calculated lattice parameters, band gaps, and magnetic ground states of Y1-xLaxTiO3 are in good agreement with available experimental data. The Ti–O–Ti bond angels increase with increasing x while the total energy difference between the AFM and FM states decreases and then is less than 0 meV. An FM-AFM phase transition is strongly favored with decrease of the GdFeO3-type distortion. The present study reproduces structural, electronic and magnetic properties of Mott insulating Y1-xLaxTiO3, and interprets well experimentally-observed magnetic phase transition.