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.

Heavy Thallium Based Fluoroperovskite TlAF3 (A = Ge, Sn and Pb) Compounds: A Computational Investigation

Combination of heavy elements in forming a stable system leads to enhancement in effective atomic number making it desirable in many applications such as detection and shielding of radiation. We present our theoretical investigations on new Thallium based heavy fluoroperovskites TlAF3 (A = Ge, Sn and Pb). The study is carried out to explore the structural, elastic, electronic, and optical properties through the Density Functional Theory (DFT) using the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method implemented in WIEN2k. Generalized Gradient Approximation with consideration of electronic correlation effects (GGA+U) was employed for calculations. The lattice constants deduced from the optimization curves were found to be in the range of 4.00 Å to 4.85 Å. Elastic properties were obtained from the calculated elastic constants. From band structure calculations, it is evident that the bandgaps range from 0.84 to 1.89 eV. All the studied compounds exhibit indirect bandgap nature. Fluorine atom contributes significant number of electronic states in valence and conduction bands of all studied compounds. The optical response in terms of refractive index, extinction coefficient, optical conductivity, reflectivity, and absorption coefficients are calculated and discussed in the energy range of (0-20) eV. The properties of compounds in this study are being reported for the first time.

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.

First principles study of the structural, electronic, optical and thermodynamic properties of cubic quaternary Al x In1−x P y Bi1−y alloys

The non-relativistic full potential linearized augmented plane wave (FP LAPW) method was applied to investigate the structural, electronic, optical and thermodynamic properties of (ZB)-AlP, AlBi, InP and InBi compounds and their ternary Al x In1−x P, Al x In1−x Bi, AlP x Bi1−x and InP x Bi1−x and the ordered Al x In1−x P y Bi1−y quaternary alloys. For the exchange-correlation potential, the LDA, GGA and WC-GGA have been used to calculate structural parameters. The TB-mBJ approximation was used to compute the band structures. Our results for binary compound agree well with available data found in literature. The lattice constants and the bulk modulus versus compositions x and y deviate from the linearity. All quaternary alloys are semiconductors with direct band gap with the exception for Al0.25In0.75P0.25Bi0.75 and Al0.25In0.75P0.50Bi0.50, which exhibit a half metallic character (the band gap tends to zero). Furthermore, the optical properties such as the dielectric constants, refractive index, absorption, reflectivity and the energy loss have been calculated and analysed in the energy range varying from 0 to 14 eV. At the end, we have investigated some thermodynamic properties, where the lattice constants, the Debye temperature θ D, the heat capacity C V and the entropy S were carried out, plotted and discussed.