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This work presents in detail the Ab-initio computational research work on the structural, elastic, electronic, and optical properties of Perovskite-type (Halide-Perovskites) barium-based MBaF3 (M = Ga and In) compounds. The work is based on density functional theory (DFT) within WIEN2K. Structurally both GaBaF3 and InBaF3 based on optimization of Birch Murnaghan fit are found to be stable. The IRelast package for the calculations of elastic constants (ECs) is employed for the computation of elastic properties. Mechanically these compounds are identified to be ductile, hard to scratch, anisotropic, mechanically stable, and demonstrate strong resistance to plastic deformation. The precise modified Becke–Johnson (mBJ) potential is employed for electronic properties. Band structures of these compounds possess an insulating nature of direct wide energy band gap of 5 eV for GaBaF3 and 5.1 eV for InBaF3 from X-X symmetries points. To know the contribution of different electronic states to the band structures, the TDOS and PDOS i-e (total and partial density of states) are exploited. The insulating direct wide band gap energy nature presented a straightforward direction to study the optical properties of these compounds. The optical properties, of both the compounds, were studied deeply in the energy range from 0 eV to 40 eV. These compounds possess high absorption and optical conduction at high energy ranges. Both materials are transparent to incident photons at low energy ranges. We have concluded from the optical properties investigations that these compounds are suited for high-frequency UV device applications. To our deep knowledge, this is the first systematic theoretical computation of MBaF3 (M = Ga and In) with structural, elastic, electronic and optical, properties that have yet to be verified experimentally.

The structural, electronical, elastical, Debye temperatures and magnetic calculations of the FeWGa half-Heusler compounds were calculated for Type I, Type II and Type III phases by using WIEN2k. The ferromagnetic state of Type II phase is energetically more stable than types. The band gaps were obtained only in Type II phase when GGA and TB_mBJ methods were used. The total magnetic moments were calculated as 1.005, 0.876, and 2.852 μB/f.u. for Type I, Type II and Type III, respectively. However, when TB_mBJ method was used, the total magnetic moment of Type II phase was obtained as 1.00 μB/f.u., which was compatible with Slater-Pauling rule. According to the elastically calculations, Type II and Type III phases are stable, anisotropic and ductile, while Type I phase is unstable against deformation. Then the Debye temperatures were obtained as 200.83 K, 396.11 K, and 320.34 K for Type I, Type II and Type III, respectively. The FeWGa compound has 541.29 K and 396.11 K Curie and Debye temperatures, respectively. Therefore, it is an ideal compound that can be used in spintronic applications.

The aim of this paper is the prediction of the structural, electro-magnetic and mechanical properties of the Co2HfZ (Z = Al, Ga, Si and Sn) full Heusler compounds using a full-potential linearized augmented-plane wave method (FP-LAPW) based on the Wien2k program. For the structural and mechanical properties, we used the Perdew-Burke-Ernzerhof Generalized Gradient Approximation (PBE-GGA) and modified Becke and Johnson (mBJ) schemes to compute the fundamental parameters. The latter was employed for the electro-magnetic properties, to calculate the band structures (BS) and density of states (DOS) of these compounds. Our results showed the half-metallicity of Co2HfZ (Z = Al, Ga, Si and Sn). The obtained energy revealed that these alloys were thermodynamically stable and could be hence elaborated experimentally. The mechanical properties indicated that our compounds were anisotropic ductile materials. Our findings greatly support that these compounds are highly attractive potential candidates for electro-spintronic applications.

In the present work, we performed ab initio calculation to observe the doping effect of Ca on material properties of MgGeN 2 within the framework of Density Functional theory. This theory is embodied in Wien2k code. The Perdew Burke Generalized Gradient Approximation (PBE-GGA) is used as exchange-correlation potential for yielding accuracy in results. This approximation is based on the Full Potential Linear Augmented Plane Wave (FP-LAPW) method. The crystal structure, band structure, total and partial density of states (DOS) spectra which are computed for the supercell of Mg 0.875 Ca 0.125 GeN 2 . The dielectric tensor, absorption coefficient, refractive index, and reflectivity are computed for illustrating the optical properties of Mg 0.875 Ca 0.125 GeN 2 . The obtained results indicate that Ca reduces the bandgap of MgGeN 2 and makes it an attractive material for photovoltaic applications.

Semiconductor perovskite material has given important interest as a potential thermoelectric material (TE) due to its large thermopower (Seebeck coefficient, S). VScO3 Semiconductor Perovskite is investigated by the Density Functional Theory (DFT) using full potential linearized augmented plane wave (FP-LAPW) method with mBJ approximation. The energy band structure obtained from WIEN2k calculations is used to calculate the transport coefficients via the semi-classical Boltzmann transport theory with constant relaxation time (τ) as employed in the BoltzTraP package. VScO3 semiconductor perovskite is considered as a potential candidate for thermoelectric application. The calculated elastic constants show that VScO3 perovskite suitably verify Born's mechanical stability criteria and characterized by ductile manner.

In this paper, we reported a computational study of the 2-D nanomaterial (SnSi) as a possible new nanomaterial to be synthesized. This study is chiefly based on density functional theory calculation, which is implemented in the wien2k code. In fact, we calculated the electronic properties such as electronic band structures, band gaps, DOS, formation energy, and electrical conductivity of three types of monolayers Stana-Silicene; (SnSi, SnSi3, and SnSi7) with various concentrations (50%, 25%, and 12.5%) of the Sn and the Tin atoms. By computing the formation energy of these materials within various concentrations of the Sn atoms, we observed that the SnSi monolayer has more stability than SnSi3 and SnSi7. Another important result is that the electrical conductivity of SnSi depends on the concentrations of the Sn atoms. Indeed, it increases by increasing the concentration of the Sn atoms. By using various concentrations of the Tin atoms, we found out that all these nanomaterials behave as a semiconductor material within direct electronic band gaps.

The present work investigates the less explored thermoelectric properties of the n-type GaN semiconductor by combining both experimental and computational tools. The Seebeck coefficients of GaN epitaxial thin films were experimentally measured in the wide temperature range from 77 K to 650 K in steps of ∼10 K covering both low and high-temperature regimes as a function of the carrier concentration (2 × 1016, 2 × 1017, 4 × 1017 and 8 × 1017 cm-3). The measured Seebeck coefficient at room temperature was found to be highest (-374 μV K-1) at the lowest concentration of 4 × 1016 cm-3, and decreases in magnitude monotonically (-327.6 μV K-1, -295 μV K-1, -246 μV K-1 for 2 × 1017, 4 × 1017, 8 × 1017 cm-3, respectively) as the sample carrier concentration increases. The Seebeck coefficient remains negative in the entire temperature range under study indicating that electrons are the dominant carriers. To understand the temperature-dependent behaviour, we also carried out the electronic structure and transport coefficient calculations using the Tran-Blaha modified Becke-Johnson (TB-mBJ) potential and semiclassical Boltzmann transport theory implemented in WIEN2k and BoltzTraP code, respectively. The experimentally observed carrier concentrations were used in the calculations. The estimated results obtained under constant relaxation time approximations provide a very good agreement between the theoretical and experimental data of Seebeck coefficients in the temperature range from 260 to 625 K.

WloopPHI is a Python code that expands the features of WIEN2k, a full-potential all-electron density functional theory package, by the characterization of Weyl semimetals. It enables the calculation of the chirality (or "monopole charge") associated with Weyl nodes and nodal lines. The theoretical methodology for the calculation of the chirality is based on an extended Wilson loop method and a Berry phase approach. We validate the code using TaAs, which is a well-characterized Weyl semimetal, both theoretically and experimentally. Afterwards, we applied the method to the characterization of YRh$_6$Ge$_4$ and found two sets of Weyl points (ca. 0.2 eV below the Fermi energy) together with a topological nodal line (protected by mirror symmetry) crossing the Fermi energy and mapped their chiralities., 31 pages, 9 figures

In this work, we have investigated the structural, electronic and thermodynamic properties of GaP $$_{1-x}$$ Sb $$_{x}$$ and AlP $$_{1-x}$$ Sb $$_{x}$$ ternary alloys for a number of ordered structures and compositions in a series of first-principles calculations within the density functional theory, using full potential-linearised augmented plane-wave (FP-LAPW) method, as implemented in the WIEN2k code. The exchange-correlation effect was treated within the generalised gradient approximation (GGA) in the form of GGA-PBEsol to optimise the structure and to compute the ground-state properties. In addition to the GGA, the modified Becke–Johnson (mBJ) potential coupled with the spin-orbit interaction (SOI) was also applied to obtain reliable results for the electronic properties. Our investigation on the effect of composition on lattice constant, bulk modulus and band gap showed almost nonlinear dependence on the composition. The GaP $$_{1-x}$$ Sb $$_{x}$$ and AlP $$_{1-x}$$ Sb $$_{x}$$ alloys are found to be semiconductors with a positive energy gap for the whole concentration range. The spin-orbit splitting $$\Delta _{\mathrm {SO}}$$ was found to increase with Sb composition with a marginal bowing parameter. Besides, a regular-solution model was used to investigate the thermodynamic stability of the alloys which mainly indicates a phase miscibility gap. In addition, the quasiharmonic Debye model was applied to analyse the effect of temperature and pressure on the Debye temperature and heat capacity.

In this paper, we have investigated the structural, elastic, electronic, and thermoelectric properties of chalcopyrite B2BiN using the first-principles calculations via the density functional theory (DFT) implemented in wien2k code. We negative the energy formation founded indicates the stability of these alloys in ambient conditions. The obtained results predict that the studied system shows a brittle and stiff behavior based on the analysis of the elastic constants and their derived parameters such as Young’s modulus (220–240 GPa), Poisson’s ratio (0.163–0.188), and the Debye temperature (503.33 K). Moreover, the compound has an indirect bandgap of 1.37 eV, which is close to the ideal value of 1.40 eV for the solar light absorber. Its merit factor (ZT) varies from 0.96 and 0.92 for temperatures ranging between 300 and 900 K and a high value of the Seebeck coefficient (S) of 2750 μV/K at 300; these two important parameters allow the B2BiN structure to have an improvement in thermoelectric performance and can be a potential candidate for solar panel devices. To the best of our knowledge and according to the researches available in the literature, there are no experimental and theoretical studies on elastic and thermoelectric properties of B2BiN.

An ab initio study is presented on the structural and electronic properties of ZnO and MgO binaries compounds and theirs ternary alloys Zn 1- x Mg x O at various concentrations of Mg (x=0.25, 0.5 and 0.75) in wurtzite phase. We use a Wien2k package with a first principle calculation using the generalized gradient approximation (PBE-GGA) including novel exchange - correlation potentials, namely the modified Becke-Johnson (mBJ). The obtained results of structural parameters were compared with other experimental and theoretical works and it's found that they are in a good agreement. Moreover, the electronic results show that the crystal is a semiconductor with a direct band gap structure, and in the density of states (DOS) the major contribution comes by Zn-3d, O-2p and Mg-3s states.

The structural stability and optoelectronic properties of the ternary Ba1−xBexS alloys along with the pure binary compounds BaS and BeS in the rock-salt (B1) and zinc-blende (B3) phases were investigated by the density functional theory (DFT) within the full-potential linearized augmented plane wave (FP-LAPW) method implemented in the Wien2k package. The generalized gradient approximation of Wu and Cohen (WC-GGA) was used for the exchange-correlation potential (Vxc) to compute the equilibrium structural parameters, lattice constant (a), and bulk modulus (B). In addition to the GGA approach, the modified Becke-Johnson potential of Tran and Blaha (TB-mBJ) scheme coupled with the spin-orbit interaction was used to calculate the band gap energies. Results reveal that BaS, Ba0.75Be0.25S, and Ba0.5Be0.5S compounds are stable in the rock-salt phase, while Ba0.25Be0.75S and BeS are found to be stable in the zinc-blende phase. The computed results for the band structures and optical constants are compared with other available theoretical calculations and experimental measurements.

Theoretical calculations are performed to investigate the electronic, structural and optical properties of double perovskite oxide A2ZnTeO6 (A = Ca, Sr, Ba). The calculations are based on the Density Functional Theory (DFT) using the WIEN2k code. The exchange–correlation potential is treated with generalized gradient approximation (GGA-PBE). Additionally, the Tran Blaha modified Becke-Johnson exchange potential (TB-mBJ) is employed for electronic and optical calculations due to that it gives very accurate results of band gap in solids. In order to estimate the ground state parameters, total energies are calculated with respect to cell volume. Also, the energies are fitted with Murnaghan equation of state. The estimated ground state parameters are comparable with the available experimental data. The band structure calculations reveal that these compounds exhibit semiconducting behavior with a direct band gap. To explore the optical transitions in these compounds, the real and imaginary parts of the dielectric function are analyzed at ambient conditions and the important optical constants are calculated and discussed.

With the advancement of satellite imaging, aircraft, drones and more, we see the development of powerful infrared sensors, so that the human body's heat waves can be seen by the satellites.Sensing the Infrared rays of the living creatures using some recently developed and very sensitive sensors has made it easy to track the movement of human groups. By installing these sensors into photographic cameras and tuning it between 8-14 micrometer, it is even possible to obtain the exact position of the human targets from satellites. Based on the density functional theory (DFT) implemented in SOD program (Site Occupancy Disorder) and Wien2k code, we could reach to a desirable percentage of the dopant that is prefect for absorbing infrared rays. By using this information, we have synthesized Ni-Al co-doped ZnO (NiAl:ZnO) from a metal nitrate precursor and nitric acid by a modified sole-gel combustion method.

Titanium dioxide TiO2 is one of the important oxide materials used in optoelectronic industry and photovoltaic cells. The aim of this paper is to study the electronic, the optical and the thermoelectric properties of TiO2 at brookite, anatase and rutile phases. Our computation is based on the Density Functional Theory (DFT) approximations as implemented in Wien2k code according to the Full Potential-Linearized Augmented Plane Wave (FP-LAPW). The electronic and optical properties are estimated using the modified Beck Johnson potential (mBJ). These results are used to compute the thermoelectric transport properties with the Boltztrap package as integrated to our chosen code. Our results fit within other experimental and theoretical results and have the same behavior for the factor of merit and for the Seebeck coefficient

Recently, we have computed the structural and electronic properties of $$VSb_{2}$$ using the first-principles calculations based on the full potential linearized augmented plane wave (FP-LAPW) method implemented in WIEN2k code. These studies have shown that this material has a metallic character. In this work, we are interested in the study of thermoelectric properties of $$VSb_{2}$$ material using the semi-classical Boltzmann transport theory. The Generalized Gradient Approximation (GGA) is used in the scheme of Perdew–Burke–Ernzerhof (PBE) to treat the exchange correlation effect. Thus, we discuss in detail the temperature effect on the thermoelectric properties such as: the Seebeck coefficient, the thermal conductivity, the electrical conductivity, the electronic specific heat, the figure of merit, the power factor and the Pauli magnetic susceptibility.

We report variation of the structural, electronic and optical properties of $$\hbox {CsYbF}_{3}$$ perovskite compound in the 0–15 GPa pressure range, using density functional theory, implemented in the Wien2k code. With the increase in pressure, $$\hbox {CsYbF}_{3}$$ crystal squeezes while its cubical symmetry remains unbroken. The calculated electronic properties reveal that $$\hbox {CsYbF}_{3}$$ has a narrow direct band gap of 0.98 eV. The band gap, however, decreases with increase in pressure, and at 15 GPa, $$\hbox {CsYbF}_{3}$$ shows metallic behavior. This reveals the high sensitivity of $$\hbox {CsYbF}_{3}$$ to pressure increase. Furthermore, the calculated pressure-dependent optical properties of $$\hbox {CsYbF}_{3}$$ would find interesting place in optoelectronic devices.

Theoretical calculations of Al0·75Co0·25Sb diluted magnetic semiconductor (DMS) were investigated by using both GGA and TB_mBJ methods. First, the energy-volume optimization curves of AlAs and Al0·75Co0·25Sb compounds were plotted and the ferromagnetic (FM) phases were observed to be more energetically stable. The spin-up states showed metallic properties while the spin-down states had a semiconductor nature. While these properties did not change, some differences were observed in the band gap values. Fermi energies were calculated as 0.298 and 0.462 R y and band gap values were obtained as 0.229 and 0.855 eV by using GGA and TB_mBJ methods, respectively. The values of the total magnetic moments did not change and they were obtained as 2.00 μB/f.u. in both methods. Finally, the elastic properties of Al0·75Co0·25Sb compound were calculated. According to these results, Al0·75Co0·25Sb compound is a brittle half-metal ferromagnetic material and it is suitable for use in spintronic applications.

Different properties such as the structural, elastic, thermal, electronic, magnetic as well as the Curie temperature and the formation energy of the cubic perovskites PrXO3 compounds (X = V, Cr, Mn, and Fe) are studied by using the density functional theory based on the full-potential linearized augmented plane wave with local orbitals method with the generalized gradient approximation (GGA) for the exchange correlation potential as applied in WIEN2k code. The GGA + U approximation is also used to treat the f-states of Pr atoms and d-states of X atoms. We have also applied the analytical techniques for the structural parameters. The calculated structural parameters by both methods are in good agreement with experimental results. The calculated critical radii of the compounds exhibit ion conductivity as well as oxygen migration. The PrVO3, PrCrO3 and PrFeO3 compounds have a ductile nature, while PrMnO3 is brittle. The calculated electronic properties reveal the metallic nature for the studied compounds. Double cell optimizations, density of states as well as magnetic moment confirm that these compounds are ferromagnetic metals. The negative value of formation energy confirms the stability of these compounds. Large and small values of Curie temperature in these compounds show strong and weak interaction among the magnetic atoms, respectively.

A theoretical study of structural and electronic properties of chalcopyrite semiconducting materials is presented using the full-potential linearized augmented plane wave method implemented in Wien2k computational package. In this approach, the Generalized Gradient approximation was used for exchange correlation potentials. Our interest in these semiconductor materials is motivated by their promising roles in the manufacture of thin-film solar cells because of their interesting structural and electronic properties.

The technology of photovoltaic energy conversion is essentially based on semiconductors that have different physical properties, which consequently result in photovoltaic panels of different yield and lifespan but also different costs. Among these semiconductors, those belonging to the chalcopyrite family have attracted the attention of researchers around the world given their very varied physical behaviours and their syntheses, which are not too complicated. In this work, we are interested in MgGeAs2-chalcopyrite. This compound has been studied in detail by several authors except that several physical properties remain unknown including some of its elastic properties and the effect of hydrostatic pressure on its mechanical stability and its narrow band-gap. The study has been carried out with FP-LAPW method as implemented in WIEN2k code. The found results for the structural properties are in good agreement with the previous results. Structural parameters allow the determination of the elastic constants under different pressures. The mechanical stability of this compound has been studied. The value of band-gap energy of this compound has been obtained by several methods including TB-mBJ and GLLB-SC. Optical properties are also the subject of our work, from which the dielectric function and the absorption coefficient of this compound have been analyzed.

Der Schwerpunkt dieser Arbeit liegt auf der Untersuchung kubisch-tetragonaler Phasenübergänge in Perowskiten, wobei speziell PbTiO3, RbCaF3 und BaTiO3 unter verschiedenen Aspekten einer sehr detaillierten Untersuchung unterzogen worden sind. Im ersten Projekt wurde der Phasenübergang in PbTiO3 mit Hilfe einer Kombination aus Dichtefunktionaltheorie und einer kürzlich konstruierten Erweiterung der Landau-Theorie zu endlichen Drücken untersucht. Dieser Ansatz ermöglicht auch die Bestimmung der vollständigen tetragonal-kubischen Phasengrenze in der (P,T)-Ebene einschließlich einer numerischen Lokalisierung des trikritischen Punktes. Es zeigt sich, durch eine sorgfältige Analyse, dass die thermische elastische Referenzlinie ein wesentlicher Bestandteil für den Erfolg dieser Theorie ist. Des Weiteren wurden die strukturellen, elastischen und elektronischen Eigenschaften sowie die Gitterschwingungen von RbCaF3 in der kubischen sowie der tetragonalen Phase mittels ab-initio Dichtefunktionaltheorie untersucht. Zunächst wurde die Wirkung verschiedener Austauschkorrelationsfunktionale der verallgemeinerten Gradientennäherung auf strukturelle Eigenschaften wie den Drehwinkel des CaF6-Oktaeders oder das c/a-Verhältnis der tetragonalen Gitterkonstanten analysiert. Es zeigt sich, dass man die beste Übereinstimmung mit dem Experiment für die Funktionale PBEsol und Wu und Cohen (WC) erhält. Der Zusammenhang zwischen kubischer und tetragonaler Phase durch Bestimmung des Softmode-Phonons R15′ am Rand der kubischen Zone sowie des c/a-Verhältnisses und des Oktaeder-Neigungswinkels wurde evaluiert. Um die Rolle der langreichweitigen Coulomb-Wechselwirkungen bei der LO-TO-Aufspaltung zu untersuchen, werden auch Ergebnisse für Tensoren der Born-effektiven Ladungen angegeben. Außerdem wurde der entsprechende druckinduzierte Phasenübergang bei T= 0 K untersucht, der sich im Gegensatz zum experimentell bei Raumtemperatur untersuchten strukturell analogen Hochdruckübergang bei Umgebungstemperatur von erster Ordnung als von zweiter Ordnung erweist. Die kürzlich entwickelte Landau-Theorie für endliche Verzerrungen liefert eine mögliche Erklärung für diese eigentümliche Änderung des Charakters. Schließlich wurde der kubisch-tetragonale ferroelektrische Phasenübergang von BaTiO3 mittels eines ab-initio selbstkonsistenten Phonon (SCP)-Ansatzes untersucht, der die harmonische Approximation um die Einbeziehung anharmonischer Effekte bei endlichen Temperaturen erweitert. Durch Vergleich der freien Energien der tetragonalen und kubischen Phase bei verschiedenen Temperaturen wird eine Übergangstemperatur Tc von 455 K berechnet die gut mit dem experimentellen Wert von rund 400 K übereinstimmt. Für die kubische und tetragonale Phase wurden auch die Phononenspektren bei endlicher Temperatur und die thermische Ausdehnung berechnet, welche gut mit den experimentellen Werten zusammenpassen., The focus of this thesis is the study of cubic-tetragonal phase transitions in perovskites where PbTiO3, RbCaF3, and BaTiO3 are investigated in great detail and under various aspects. In the first project, the phase transition in PbTiO3 is studied with the help of a combination of density functional theory and a recently constructed finite-strain extension of Landau theory. This approach also allows determining the full tetragonal-cubic phase boundary in the (P,T) plane including an estimate of the tricritical point. A careful analysis shows that the thermal elastic baseline is an essential ingredient to the success of this theory. Secondly, the structural, elastic, vibrational, and electronic properties of RbCaF3 in the cubic and low-temperature tetragonal phases have been studied at the ab-initio level with density functional theory. The effect of various exchange-correlation functionals of the generalized gradient approximation is investigated for structural properties like the rotational angle of the CaF6 octahedron or the c/a ratio of the tetragonal lattice constants. It is found that the best agreement with experiment is obtained with the PBEsol and Wu and Cohen (WC) functionals. The relation between the cubic and tetragonal phases is studied by monitoring the cubic zone boundary soft mode phonon R15′ as well as the c/a ratio and tilt angle. The results for the Born effective charge tensors are also reported in order to study the effect of the long-range Coulomb interactions on the LO−TO splitting. The corresponding pressure-driven phase transition is investigated at T= 0 K, which is found to be of second-order in contrast to the first-order character experimentally detected for the structurally similar high pressure transition at ambient temperature. Based on the recently developed finite strain Landau theory, a possible explanation for this peculiar change of character is given. Finally, the cubic-tetragonal ferroelectric phase transition of BaTiO3 is investigated through the first-principles self-consistent phonon (SCP) approach, which extends the harmonic approximation by incorporating anharmonic effects at finite temperatures. By comparing the free energies of the tetragonal and cubic phases at different temperatures, we obtain aTc of 455 K in good agreement with the experimental value of around 400 K. For cubic and tetragonal phases the phonon spectra and the thermal expansion are calculated at finite temperature, which are in good agreement with the experimental values.

This paper presents the structural and optoelectronic behavior of ZnSiP2 compound theoretically. The calculations are performed using full potential linearized augmented plane wave method (FP-LAPW) within density functional theory (DFT) as embodied in WIEN2K code. For the accuracy of calculation, Perdew-Burke generalized gradient approximation (PBE-GGA) is used. Based on the energy bands, the forbidden band gap of ZnSiP2 was found to be 1.37 eV which is suitable for photovoltaic applications. The formation of bands are explained with the help of spectra of density of states (DOS) to determine the effect of Ge doping at Si site on the electronic structure. We have also performed the computations for ZnSi0.875Ge0.125P2. Energy dependent absorption spectra is also reported in this paper to highlight the possible utilization of these compounds in optoelectronic devices.

Half-Heusler compounds pose unusual behavior because of their variable band gap and as well as both metallic and semi-metallic nature. These compounds can be used in different applications on the basis of band gap tenability. We have discussed the structural, electronic, elastic and magnetic properties of CoVZ (Z = Pb, Si, Sn, Ge) by using WIEN2k simulation code based on density functional theory (DFT). We have optimized the all possible structural configuration of each compound and considered which optimized with lowest energy and lowest equilibrium volume. For determination of electronic exchange correlation energy the generalized gradient approximation (GGA) is used in both platforms. We have also obtained the individual elastic constants, shear modulus, Young's moduli, B/G ratio and Poisson's ratio, which shows that these compounds are ductile except CoVGe shows little ductility. Debye temperatures are calculated by compression wave velocity, shear wave velocity and with their average value.

The first principle investigation of ZnGeAs2 has been performed using most accurate Tran-Blaha modified Becke Johnson (TB-mBJ) exchange potential. The available exchange potential is a full potential linear augmented wave (FP-LAPW) method based on density functional calculations. Band gap reported in present calculation indicates direct nature of 1.18 eV magnitude. To deduce optical behavior, properties such as imaginary component of dielectric tensor, reflectivity, refractivity and integrated absorption coefficient are computed using WIEN2k package. Optical spectra’s component i.e. parallel and perpendicular are observed to be nearly coinciding with each other. This clearly indicates isotropic nature of the material. The present band gap scale and optical response recorded for the material indicates active utilization of these compounds in optoelectronic and other photovoltaic applications.In the original version of the article supplied to AIP Publishing, Figure 2 was missing. An updated article, with this figure included, was published on 27 January 2021.

Infrared photodetectors have gained attention because of its high penetration depth of IR light. Narrow band gap semiconductors can function as photoactive materials in IR photodetector applications. Herein, a the TlN nanosheet is proposed because the TlN nanosheet has narrow band gap and the TlN nanosheet with vacancy defect is a good candidate for spintronic applications. Under the generalized gradient approximation (GGA), the vacancy defects on electronic and magnetic properties of semiconductor the TlN (thallium nitride) nanosheet have been investigated by full potential linearized augmented plane wave method (FP-LAPW) within the density function theory (DFT) implemented by the Wien2k code. The electronic band structure calculations indicate that Tl atom vacancy (VTl), N atom vacancy (VN) in the 2D TlN nanosheet leads to p-type and n-type conductivity, respectively. And mixed Tl and N atoms (VTl&N) vacancies maintain the overall neutral charge in the solid. We found that the vacancies in the TlN nanosheet induce spin polarized states in the band gap, and VTl-defect, VN-defect and VTl&N-defect induce local magnetic moments of 3.0μB, 0.3μB and 3.8μB, respectively.

Optoelectronic and thermoelectric properties of SrXO4 (X ​= ​S, Se, Te) have been investigated with the help of WIEN2K code by using FP-LAPW method and GGA approximation of the DFT approach. The obtained results show that SrSO4 and SrSeO4 are direct wide band gap semiconductors, while, SrTeO4 is an indirect band gap semiconductor. Based on theoretical study of optical properties, it has been established that the investigated compounds are promising candidates for active optical devices operating in the UV and visible range. These compounds have also been found to be weak reflectors for incident photons as they reflect up to 60% of the incident photons in the upper UV region. The semi-classical Boltzmann transport kinetic equations are used to study thermoelectric properties such as electrical conductivity, thermal conductivity, power factor, Seebeck coefficient and Figure of merit of the considered compounds. The research shows that SrSeO4 and SrTeO4 are promising compounds for thermoelectric devices.

The objective of this work is to explore structural, mechanical and thermal stability including electronic, optical and thermoelectric properties of state-of-the-art AlNiX (X = P, As and Sb) half-Heusler compounds having 18 valence electron count (VEC). Calculations have been carried out in the framework of density functional theory (DFT) implemented in WIEN2k code followed by the solution of the Boltzmann transport equation with constant relaxation time approximation. In the most energetically favorable structure, their lattice constants lie in the range of 5.501 A – 5.983 A and band gaps have been found to be 0 eV, which confirm the metallic behavior of these compounds. The different elastic and thermodynamic parameters confirm their mechanical and thermal stability with a mechanically anisotropic and ductile nature. Specific heat and entropy of these materials increase as the atomic number of X atom increases. The calculated optical parameters prove their candidature for promising photovoltaic devices and shields for UV radiation. The thermal conductivity has been computed using Slack's model. This detailed study shows that these compounds are promising for materials scientists due to their very high lattice thermal conductivity and low figure of merit. We deny recommending them as good thermoelectric applications.

The investigations on the physical properties of the Ba2NaIO6 double perovskite, in this work, are presented. These investigations are carried out using WIEN2k computational code realized within the density functional theory (DFT) approach and at the level of the generalized gradient approximation (GGA) of exchange correlational functional as parameterized by Perdew Burke and Erenzerhof (PBE) beside employing modified Becke-Johnson (mBJ) as well as hybrid Heyd-Scuseria-Ernzehof (HSE) potentials. The results obtained for structural parameters have been found well-matching to the available literature. The obtained results of the electronic structure indicate the Ba2NaIO6 has a direct bandgap semiconductor at the center of the Brillouin zone (T). We also presented a detailed study on its optical properties. Concerning its mechanical properties, the results of the bulk, Young, and shear modulus (G), the anisotropic factor (A), and Poisson's ratio ( ν ) are obtained using the first-principles results for the elastic constants. The sound velocities and Debye temperature are also determined for this compound. Furthermore, calculations of its transport properties demonstrate its p-type semiconductor nature. The results of the reported parameters show that Ba2NaIO6 double perovskite is a suitable base material for optoelectronic devices particularly working for the infrared region as well as for thermoelectric applications.

In this paper, topological phase and optical properties of bulks and nanolayers (NLs) of the ScNiX (X = Ga and In) half-Heusler compounds have been studied. The calculations have been done based on the density functional theory in the framework of the Wien2k package. The generalized gradient approximation was used for the exchange-correlation functional. Electronic structures and density of states of the bulks and NLs of the compounds show that, they are non-magnetic and metal. It is found that, the bulks of compounds don't have topological phase, but the NLs of compounds have topological phase. Thus, the NLs of both compounds are topological metals. Important optical properties of these compounds were acquired. The results show that, there is optical anisotropy in the NLs, between the in-plane (x) and out-of-plane (z) directions. The absorptions of the bulks and NLs of the compounds are high in the UV range.

The main objective of this work is the prediction of mechanical stability, magnetic and optoelectronic properties of BaCmO3-Cubic Perovskite by FP-(L)APW + lo method which is implemented in WIEN2k code. The structural parameters and the elastic constants were determined using GGA as exchange-correlation functional and the energy analysis of the most stable magnetic phase showed that BaCmO3 is ferromagnetic. The elastic properties confirmed the mechanical stability of this compound and by their knowledge; several related mechanical parameters were determined. This compound is based on Curium which has highly correlated electrons and since GGA semilocal functional does not accurately treat the electronic properties of this kind of compound, it has been corrected by the estimation of Hund’s exchange “J” and Hubbard interaction “U” parameters by two different methods that are Constrained DFT “cLDA” and constrained Random Phase Approximation “cRPA”. GW approximation with GGA + U as a starting point (GW@GGA + U) was also used for the prediction of the electronic properties of this compound and this choice is motivated by its proven success for this kind of study. The electronic properties have shown that BaCmO3-Cubic Perovskite is a half-metal with a total magnetic moment of ∼6 μB. The optoelectronic transitions between the valence band top and the conduction band bottom have been identified by an analysis of the real and imaginary part variations of the dielectric function.

This study presents the calculation of (Co-N) co-doped ZnO in the wurtzite structure of 32 atoms, a density functional calculation and a theoretical analysis of the electronic and magnetic properties are investigated using the Full-Potential Linearized Augmented Plane Wave (FPLAPW) method, implemented in WIEN2k package. We have used two approaches LSDA and LSDA+U to analyze and correct the density of state, and to understand the Co and N influence on p-type ZnO at different concentrations, i.e., their bonding with nitrogen is also determined. The results prove that ZnO doped with two N concentrations of 6.25% and 12.5% is p-type, semi-metallic and ferromagnetic caused by the strong hybridization effect between N 2p and O 2p states, with a full magnetic moment of 1μB and 0.31μB, respectively. As for co-doped ZnO with Co and two concentrations of N, the LSDA+U approximation shows that the total magnetic moment increases with the N concentration from 3.92 to 4.51μB due to hybridization effects between Co 3d and N 2p states.

In this paper, we report the results of the density functional theory (DFT)-based theoretical calculations of structural, electronic and elastic properties of HfO2 in cubic phase (c-HfO2) under pressure up to 30 GPa using full-potential linearized augmented plane wave (FP-LAPW) approach as implemented in Wien2k package. The generalized gradient approximation as parameterized by Wu-Cohen (GGA-WC) and the Tran-Blaha modified Becke-Johnson exchange potential (mBJ) with improved parameterization by Koller were used for the exchange-correlaton effect, the later was employed with objetive of obtaining accurate band gap of the compound. Our results of structural optimization are in good agreement with other available theoretical ones and experimental datas, and we found that the volume of c-HfO2 decreases with pressure. Our electronic calculations indicate that c-HfO2 has indirect band gap X-Γ whose value is 6.189 eV, and this value increases with increasing pressure. The calculated elastic properties show that this material is ductile for pressures up to 12.5 GPa, and then it becomes elastically brittle. Finally, the thermodynamic properties of c-HfO2, such as, heat capacities, thermal expansion, Debye temperature, Gruneisen parameter and entropy under high pressures and temperatures were computed using the quasi-harmonic Debye model as embedded in GIBBS2 code and analyzed in details.

Investigation of the physical properties of chalcopyrite materials using ab-initio methods have been carried out to simulate a new structure of thin-films photovoltaic cells with high conversion efficiency. The Density Functional Theory calculations have been performed using Wien2k computational package by employing the full-potential linearized augmented plane wave method. Structural and electronic properties of chalcopyrite semiconducting material Copper–Indium–Gallium–Selenium i.e. CuIn1-xGaxSe2 have been investigated using local density approximation for the exchange-correlation potential. The electronic structures and linear optical properties have been studied using both the semi-local Becke-Johnson potential and its modified form i.e. mBJ and TB-mBJ. Computational results are in good agreement with those acquired experimentally. The viability of alloys in realization of ultra-thin-film based (CIGS) solar cells with high performance has been proposed after simulation and analysis study using one of solar cell simulation tools. The studied material exhibits capability to become a promising candidate for fabrication of optoelectronic and photovoltaic devices.

In this paper, we estimate the bandgaps, absorption coefficients, and cost of 1KW capacity of solar photovoltaic (PV) module of ternary chalcogenides materials AB2X4 (A = Zn, Cd; B = Ga; X = Te). The absorption integrated coefficient calculations using density functional theory (DFT) under Wien2k modeling (Blaha et al. in Wien2K code, an augmented plane wave plus local orbitals program for calculating crystal properties. Vienna University of Technology, Vienna, Austria, 2014 [1]) have been done for proposed materials for economic analysis of solar PV module. The present investigation reveals that present material shows good capacity to absorb incoming photons in cost-effective manner rather than crystalline Si.

The half-metallic calculations of MnZrX (X = In, Tl, C, Si, Ge, Sn, Pb, N, P, As, Sb, O, S, Se Te) half-Heusler compounds were investigated using WIEN2k code. In all compounds, the ferromagnetic (FM) phases were the most stable states energetically. The spin-up electrons of all half-Heusler compounds have semiconducting nature with energy gaps while spin-down electrons have metallic behavior. According to calculated Cij elastic constants, MnZrIn, MnZrTl, MnZrSi, MnZrGe, MnZrSn, MnZrPb, MnZrP, MnZrAs, MnZrSb, MnZrS, MnZrTe half-Heusler compounds are elastically stable except MnZrC, MnZrN and MnZrO compounds. Additionally, MnZr(In, Tl, C, Si, Ge, N, P, As, Sb, S and Se) compounds are ductile and MnZr(Sn, Pb, O and Te) compounds are brittle materials. Finally, MnZr(In, Tl), MnZr(C, Si, Ge, Sn, Pb, O), MnZr(N, P, As, Sb), MnZr(S, Se, Te) half-Heusler compounds were obtained true half-metallic ferromagnets (HMF) within 4.00, 3.00, 2.00 and 1.00 µB/f.u. respectively.

We have studied the structural, electronic, and magnetic properties of Rh2Y In (Y = Nd, Sm) alloys based on rare earth elements, using the full-potential linearized augmented plane-wave method (FP-LAPW) implemented in the Wien2K computer code with the parameterization of the generalized gradient approximation (GGA) and the local density approximation (LDA). Our results reveal a metallic behavior for rare earth-based full-Heusler Rh2Y In (Y = Nd, Sm) alloys. Indeed, the structure of the state density illustrates a polarization for the up orientation (metal character) and a pseudo gap at the down orientation.

First-principles density functional theory approach is adopted to determine the electronic, magnetic and structural characteristics of the Mn2CoAs1−xAlx (x = 0,0.25,0.50,0.75) Heusler alloys. The computations are carried out by WIEN2k code based on full-potential linearized augmented plane wave method (FP-LAPW). Moreover, the exchange-correlation energy functional is treated at the level of the generalized gradient approximation (GGA). Analysis of our computed results of the electronic band structure, as well as the density of states of the Mn2CoAs compound, show it a stable and half-metallic material with an energy band gap value of 0.48 eV. The calculated spin gap values are: 0.627 eV, 0.22 eV and 0.188 eV for Mn2CoAs0.75Al0.25, Mn2CoAs0.50Al0.50 and Mn2CoAs0.25Al0.75 respectively. Furthermore, the calculated total magnetic moment of the Mn2CoAs (4 µB) is found to be in agreement with the Slater–Pauling rule. Thus, our calculations show the Mn2CoAs1−xAlx (x = 0, 0.25, 0.50, 0.75) Heusler alloys potential materials for near future applications in spintronic because of their half-metallic ferromagnetism property.