Elastic constants, electronic properties and thermoelectric response of LiAlX (X=C, Si, Ge, And Sn) half-Heusler

Since they have become indispensable in various technological applications and a powerfulsource for generating energy in thermoelectric devices, Lithium-based alloys symbolize the topicof many experimental and theoretical reports. Hence, LiAlX(X = C, Si, Ge, Sn) materials representthe main research in this study. Different interesting properties such as the effect of pressure onthe band gap as well as the elastic parameters and the thermoelectric efficiency of these materialswere investigated using the full potential linearized augmented plane wave (FP-LAPW) method.LiAlX alloys were found to be semiconducting with indirect band gaps. When studying themechanical properties, we found that LiAlC alloy is stable against a wide range of pressurechanges (90 GPa), while the rest three systems preserve their mechanical stability in a moderaterespectively range of 40, 50 and 30 GPa, respectively. The semiconducting band gap for eachpossible transition have been calculated in a range of different pressures using both GGA andmBJ-GGA approximations. The results ended up revealing a decaying trend of the indirect gapalong Г-X direction with the increase of pressure. High values of the power factor were achievedand a large figure of merit (almost 0.7 for all systems) was calculated at 600K, which makesthese Li-based alloys very auspicious in the thermoelectric field applications.

Theoretical approach to explore structural, electronic, magnetic, elastic and thermal characteristics of Heusler alloys CoYTiZ (Z = Al, Ga, Si, Ge)

In this study, structural, electronic, magnetic, elastic and thermal properties of Co-based Quaternary Heusler alloys (QHAs) CoYTiZ ([Formula: see text], Ga, Si, Ge) have been investigated by Wien2k code. The calculations have been performed using full-potential linearized augmented plane wave (FP-LAPW) method. Generalized Gradient Approximation (GGA) method has been adopted. Structural properties have been explored for three different Wyckoff positions. From the geometry optimization calculations, it is concluded that all these alloys are stable in Type-III crystal structure. Moreover, magnetic phase optimization revealed ferro-magnetic (FM) phase as stable one. Results of electronic properties have shown metallic character for CoYTiAl, CoYTiGa, CoYTiGe while nearly half metal (HM) character for CoYTiSi. Magnetic moment obeys Slater Pauling rule (SP) for these alloys. To check out the mechanical stability, elastic properties have been investigated. Elastic parameters have shown the ductile nature of these alloys. The values for melting temperature ([Formula: see text] have confirmed the thermal stability of the studied alloys.

First-Principles Predictions on Structural Stability, Electronic, Optical, and Thermal Properties of Semiconductors GaNxAs1-x: Materials for Futuristic Optoelectronic Energy Devices

The knowledge of the physical properties of a material is crucial to realize its practical technological applications.Here, a study related to phase stability, transition pressure, electronic, optical,and thermal propertiesof GaAs, GaN, as well as their mixed ternary alloys GaN0.25As0.75, GaN0.5As0.5, andGaN0.75As0.25 is presented. The study is performed by employing "full-potential linearized augmented-plane-wave plus local-orbital, (FP-L(APW+lo))approach framed within density functional theory (DFT)" and recognized within WIEN2k computational code. The results of the phase stability show that the GaNxAs1-x alloys are stable for all compositions in the zinc blendephase (B3),except for x=1,, whereas the structure corresponding to x=1 composition is found to be more stable inthe wurtzite (B4) phase. The physicalproperties of the more stable phases corresponding to each composition are explored. The pressure-induced phase transition is also investigatedcorresponding to each composition. The electronic and optical properties are investigated using the Tran-Blahamodified Becke-Johnson (mBJ) potential approach. To explore the thermal properties, the "quasi-harmonic Debye model" approach is employed. Our calculated results of the absorption coefficients and optical band gap show that these alloys could be appropriate candidates for applications in solar cell and optoelectronic devices.

First Principles Investigation of the Optoelectronic Properties of Molybdenum Dinitride for Optical Sensing Applications

The electronic and optical properties of the newly synthesized molybdenum dinitride (MoN2) in the hypothetical 2H structure analogous to MoS2 is investigated using the density functional theory (DFT) full potential linearized augmented plane wave (FP-LAPW) method and the modified Becke–Johnson (mBJ) approximation. The aim is to investigate the optoelectronic properties of this compound for potential optical sensing applications and compare with the capabilities of MoS2 in this field. As compared to MoS2, which is a semiconductor, MoN2 is found to be a semi metal from the band structure plots. The dielectric function, optical conductivity and the optical constants, namely, the refractive index, the reflectivity, the extinction and absorption coefficients, are evaluated and compared with those of MoS2 and discussed with reference to the sensing performance.

Calculation of Structural, Electronic and Optical Properties of Double Perovskite Ca2CrNbO6

The structural electronic and magnetic properties of the double perovskite Ca2CrNbO6 in the cubic structure are investigated using the empirical full-potential linearized augmented plane wave (FP-LAPW) method within the framework of the spin-polarized density functional theory (DFT). These properties are calculated using the Generalized Gradient Approximation (GGA), [Formula: see text] and modified Becke–Johnson mBJ-GGA. In addition, the real and imaginary parts of the optical dielectric function and the reflectivity, and the refractive spectra are computed and the main features shown by their spectra are ascertained on the base of the investigation of density of states.

Electronic, magnetic and optical properties of XScO3 (X=Mo, W) perovskites

The density functional theory (DFT) full potential linearized augmented plane wave (FP-LAPW) method with the modified Becke–Johnson (mBJ) approximation is used to perform spin polarised calculations of the transition metal perovskites MoScO3 and WScO3. Both depict half metallic behaviour with semiconducting and metallic in the minority and majority spins respectively. MoScO3 and WScO3 have indirect R− Γ band gaps in the minority spin channels of 3.61 and 3.82 eV respectively. Moreover, they both show substantial integer magnetic moments of 3μB with 100% spin polarization typical to half metals. In addition, we calculate the dielectric function, optical conductivity and the optical constants, namely, the refractive index, the reflectivity, the extinction and absorption coefficients.

Електронна будова та магнітні властивості сплавів Гейслера: MMnSb (M = Ni, Pd, Pt)

Методами зонних розрахункiв у моделi FLAPW (the full-potential linearized augmented-plane-wave) отримано iнформацiю про енергетичнi, зарядовi та спiновi характеристики сплавiв MMnSb (M = Ni, Pd, Pt). Отриманi данi свiдчать про те, що за рахунок росту ковалентної взаємодiї атомiв когезiйнi енергiї зростають у послiдовностi сплавiв PdMnSb → NiMnSb → PtMnSb, а самi сплави феромагнiтно впорядкованi, з пiдвищеною локалiзацiєю магнiтних моментiв на атомах марганцю. Отримано, що основний внесок у формування магнiтних моментiв сплавiв дають 3d-електрони атомiв марганцю. При цьому домiнуюча роль його електронiв припадає на t2g- i в меншiй мiрi eg-орбiталi. Внески ж s,p-електронiв марганцю i електронiв iнших атомiв у формування магнiтних моментiв сплавiв виявляються малими.

Structural, electronic, optical and thermoelectric analysis of Rb/Cs2TeBr6 Vacancy ordered double perovskites

It is compulsory to develop technologies able to generate energy at negligible cost to the environment. Therefore, in present work, lead free vacancy ordered double perovskites Rb/Cs2TeBr6 were reported as green energy materials on basis of full potential linearized augmented plane wave method calculations. The study has been carried out in terms of structural, electronic, optical and thermoelectric properties. It was noted from values of tolerance factor and formation energy that both Rb/Cs2TeBr6 compounds are stable in perovskite structure. The band gaps were calculated in close resemblance with experiments. These values (2.09 eV Rb2TeBr6 and 2.10 eV for Cs2TeBr6 with EV-GGA) were examined in visible range of electromagnetic spectrum. The optical properties such as real and imaginary parts of dielectric function, optical conductivity and reflectivity ensured the use of Rb/Cs2TeBr6 compounds for solar cell applications. Also, the reasonable values of Seebeck coefficients and figure of merit proposed the studied compounds for thermoelectric power generation.

THE FIRST PRINCIPLE STUDY OF COMPARISON OF DIVALENT AND TRIVALENT IMPURITY IN RRAM DEVICES USING GGA+U

Resistive switching (RS) performances had prodigious attention due to their auspicious potential for data storage. Oxide-based devices with metal insulator metal (MIM) structure are more valuable for RS applications. In this study, we have studied the effect of divalent (nickel) as well as trivalent (aluminum) dopant without and with oxygen vacancy (V[Formula: see text] in hafnia (HfO[Formula: see text]-based resistive random-access memory (RRAM) devices. All calculations are carried out within the full potential linearized augmented plane-wave (FP-LAPW) method based on the WIEN2k code by using generalized gradient approximation (GGA) and generalized gradient approximation with U Hubbard parameters (GGA+U) approach. The studies of the band structure, density of states and charge density reveal that HfNiO2+Vo are more appropriate dopant to enhance the conductivity for RRAM devices.