WIEN2k Code Research Articles

Theoretical investigation of the physical properties of cubic perovskite oxides Sr[formula omitted] ([formula omitted] Sc, Ge, Si)

Various physical properties (electronic, optical and thermoelectric) of cubic perovskite oxides SrXO3 (X= Sc, Ge, Si) are investigated by using the density functional theory (DFT) within Wien2K code. This code is based on different approximations such as generalized gradient approximation GGA, PBEsol, LDA, WC and the modified Becke–Johnson exchange potentials (mBJ, nmBJ and unmBJ). Structural properties and the optimization have been calculated using PBEsol functional which showed a significant results that are in good agreement with the experimental ones. The results for physical properties such as electronic, thermoelectric and optical are analyzed in detail by using the nmBJ approximation. The obtained results present an opening gap for SrSiO3, SrGeO3 and a metallic behavior for SrScO3. An average of transmittance which is about 94% to 97% was observed in the range of visible light. The increase of electrical conductivity with temperature confirms the effect of thermal agitation on the concentration of charges carriers using BolzTrap2 Package. Lastly a phonon dispersion was made and show that for X= Ge and Si, the structure is relatively stable while SrScO3 is dynamically unstable. These results prove the ability that these materials can be exploited in many applications and manufacturing of optoelectronics for Sensors.

Half-metallic behavior Co2YAl (Y= Mo,Tc) compounds

The present manuscript reports structural stability, half-metallic behavior, thermophysical and thermoelectric properties of Co2MoAl and Co2TcAl full Heusler compounds using first-principle calculations. The full-potential linearized augmented plane wave method within the framework of density functional theory is implemented and WIEN2k code is incorporated in the stable Fm- 3m phase to attain the desired results. The L21 phase is found as the most stable phase for both compounds. The optimized equilibrium lattice parameters in the stable phase are 5.89Å, 5.86Å for Co2MoAl and Co2TcAl respectively. The electronic band structure study proves that both compounds Co2MoAl and Co2TcAl have indirect band gaps of 0.74eV and 0.85eV respectively in majority spin alignment. The half-metallic performance of the present set of compounds is explained by the spin-resolved density of states. The Fermi level at the Brillouin zone point approves the metallic as well as semiconducting behavior. To elucidate the thermodynamical stability of these materials against pressure and temperature by implementing the quasi-harmonic approximation of various parameters like Debye temperature, Gruneisen parameters and specific heat are studied successfully. To know the thermoelectric response, Seebeck coefficient and electrical conductivity are computed using the BoltzTrap code. The thermodynamic profile delivers that the present set of compounds possesses no anomalies with respect to the phase transition or instabilities. The computational study insights that the compounds can be synthesized experimentally and find a route towards spintronic and thermoelectric applicability.

Half-metallic behavior Co2YAl (Y= Mo,Tc) compounds

The present manuscript reports structural stability, half-metallic behavior, thermophysical and thermoelectric properties of Co2MoAl and Co2TcAl full Heusler compounds using first-principle calculations. The full-potential linearized augmented plane wave method within the framework of density functional theory is implemented and WIEN2k code is incorporated in the stable Fm- 3m phase to attain the desired results. The L21 phase is found as the most stable phase for both compounds. The optimized equilibrium lattice parameters in the stable phase are 5.89Å, 5.86Å for Co2MoAl and Co2TcAl respectively. The electronic band structure study proves that both compounds Co2MoAl and Co2TcAl have indirect band gaps of 0.74eV and 0.85eV respectively in majority spin alignment. The half-metallic performance of the present set of compounds is explained by the spin-resolved density of states. The Fermi level at the Brillouin zone point approves the metallic as well as semiconducting behavior. To elucidate the thermodynamical stability of these materials against pressure and temperature by implementing the quasi-harmonic approximation of various parameters like Debye temperature, Gruneisen parameters and specific heat are studied successfully. To know the thermoelectric response, Seebeck coefficient and electrical conductivity are computed using the BoltzTrap code. The thermodynamic profile delivers that the present set of compounds possesses no anomalies with respect to the phase transition or instabilities. The computational study insights that the compounds can be synthesized experimentally and find a route towards spintronic and thermoelectric applicability.

Structural stability, mechanical, and optoelectronic properties of A2TlBiI6 (A = Cs and Rb) for energy harvesting: A first principles investigation

Halide double perovskite materials have potential application in renewable energy devices. Herein, the optoelectronic properties and mechanical stability of A2TlBiI6 (A = Cs and Rb) determined using density functional theory utilizing WIEN2k code have been presented. The traditional and recently modified versions of the tolerance factors have helped identify these compounds as structurally stable, whereas the enthalpy and positive values of the frequency of phonon dispersion indicate the dynamical stability of these perovskite materials. Density of states and band structure calculations indicate that the electronic transition occurs from the top of the valence band [Tl(6p)+Bi(6p)+I(5s)] to the bottom of the conduction band [Tl(6p)+Bi(6p)]. These electronic transitions are responsible for inherently direct band gap at the Γ-point of the first Brillouin zone. The energy band gap calculations for Cs2TlBiI6 and Rb2TlBiI6 give direct band gap values of 2.0 and 2.1 eV, respectively. Our results show that Tl–Bi based double perovskites exhibit considerable stability, suitable band gaps, and excellent light absorption. In particular, direct band gap materials are very promising for use in a multi-junction solar cell. We hope that our work will stimulate the interest of experimental and theoretical experts to synthesize new materials for the solar industry.

Structural, phonon, thermodynamic, and electronic properties of MgFeH3 at different pressures: DFT study

The main objective of this work is to improve the kinetic properties and desorption temperature of MgFeH3 by applying different pressures with the help of the WIEN2k code. We have theoretically determined that MgFeH3 has a 3.64 wt% gravimetric hydrogen storage capacity. The formation energy and desorption temperature of MgFeH3 significantly improve with increasing pressures. Phonon dispersion curves predict that the stability of the compound decreases with increasing pressure. Electronic properties show the metallic nature of the studied compound at all pressures. At the same time, DOS shows that d-states of Fe move from the valence to the conduction band with increasing pressures. In thermodynamic properties, we have calculated entropy, specific heat at constant pressure (Cp), thermal expansion coefficient (α) as well as Debye temperature (θD). Optical properties are also calculated for 0–100 GPa pressures in terms of absorption of light energy in visible to ultraviolet regions, refractive index, reflectivity spectrum, and optical conductivity.

Theoretical investigation of fundamental physical properties of full-Heusler Co2VZ (Z= Al, Bi, Ga, Ge) compounds

A subclass of ternary intermetallic known as Heusler compounds is being employed in the steel industry to increase material strength. This study examines the structural, electrical, optical, and magnetic properties of Co2VZ (Z=Al, Bi, Ge, Si) compounds using two different methods. First is full potential linearized augmented plane wave (FP-LAPW) method by WIEN2k and second is pseudo potential method by Atomic Tool Kit-Virtual Nano-Lab. The equivalent energy gaps in the minority-spin of Co2VZ (Z= Al, Bi, Ga, Ge) with WIEN2k code, which displays 100% spin polarization, are 0.703, 0.384, 0.186, and 0.67 eV near to the Fermi level. Furthermore, it is discovered that these compounds are absolutely half-metallic ferromagnetic (HMF). With the exception of Co2VBi, which exhibits metallic properties, the aforementioned compounds exhibit 0.525, 0.0, 0.553, and 0.786 eV band gaps in the ATK-VNL code and indicate 100% spin polarization. The magnetic moments of the compounds Co2VZ (Z= Al, Bi, Ga, Ge) are found to be 2.976, 4.003, 1.989, and 3.001 µB, respectively, in the WIEN2k code. The relative magnetic moments of the aforementioned compounds are also 1.991, 3.947, 1.999, and 2.997 µB, according to the ATK-VNL code.

Investigation of the electronic and thermoelectric properties of nitrogen chains doping SWCNT: ab initio study

In this work, we have investigated the electronic and thermoelectric properties of CN, C2N2 and C4N2 nanotubes resulting from doping of nitrogen atoms, three and two N-zigzag chains on small (3,3) single walled carbon nanotube (SWCNT) respectivelly. All calculations were performed via DFT theory using WIEN2K code. The electronic structure calculations were done using GGA with TB-mBJ exchange potential, while the thermoelectric calculations were done using semi-classical Boltzmann transport theory. The results show that all structures are energetically stable. The electronic behaviour of (3,3) SWCNT transforms from semiconductor to metal in CN nanotube and to topological Weyl semimetal (WSM) state for C2N2 and C4N2 nanotubes. The calculations of thermoelectric properties, including electrical conductivity, Seebeck coefficient and power factor, reaveal that the N-doping enhances the thermoelectric properties of pristine nanotube. SWCNT with nitrogen doping has promising electronic and thermoelectric capabilities that make it a potential for electronic and thermoelectric devices.

Appealing perspectives of the structural, electronic, elastic and optical properties of LiRCl3 (R = Be and Mg) halide perovskites: a DFT study.

To enhance the effectiveness of materials, we are motivated to investigate lithium-based halide perovskites LiRCl3 (where R = Be and Mg) using first-principles techniques based on density functional theory (DFT), implemented in the WIEN2K code. In this study, the research makes use of the WIEN2K simulation code, employing the plane-wave and self-consistent (PWSCF) approach. The cut-off energy, responsible for distinguishing core and valence states, is established at -6.0 Ry. To guarantee well-converged solutions with 2000 K points, parameters of RMT × Kmax = 7.0 are selected, where RMT represents the smallest muffin-tin radius and Kmax denotes the plane wave cut-off. Convergence is determined to be attained when the overall energy of the system remains unchanged during self-consistent calculations, reaching a threshold of 0.001 Ry. We observe structural stability of these materials using the Birch-Murnaghan fit, tolerance factor and formation energy. The tolerance factor for LiMgCl3 and LiBeCl3 are 1.03 and 0.857, while the formation energy for LiMgCl3 and LiBeCl3 are -7.39 eV and -8.92 eV respectively, confirming these to be stable structurally. We evaluate the electronic properties of the current materials, shedding light on their nature, by using the suggested modified Becke-Johnson potential. It turns out that they are indirect insulators, with calculated band gaps of 4.02 and 4.07 eV for LiMgCl3 and LiBeCl3, respectively. For both materials, we also calculate the density of states (DOS), and our findings regarding the band gap energies are consistent with the band structure. It is observed that both materials exhibit transparency to low-energy photons, with absorption and optical conduction occurring in the UV range. These compounds are mechanically stable, according to the elastic investigation, however LiBeCl3 shows higher resistance to compressive and shear loads as well as resistance to shape change. On the other hand, LiMgCl3 exhibits weaker resistance to changes in volume. Furthermore, we discovered that none of the compounds are entirely isotropic, and specifically, LiMgCl3 and LiBeCl3 are brittle in nature. These materials appear to be potential candidates for use in optoelectronic devices based on our analysis of their optical properties. Our findings may provide comprehensive insight, invoking experimental studies for further investigations.

Physical, optoelectronic and thermoelectric characteristics of double perovskite (Sr2ScBiO6) for green energy technology using ab initio computations.

This work presents the investigation of physical characteristics including structural, electronic, elastic, optical and thermoelectric, of the double perovskite (DP) oxide Sr2ScBiO6 with the aid of the FP-LAPW method, dependent on DFT combined with BoltzTraP code. To incorporate the inclusion of exchange as well as correlation effects, approximations like LDA and three different forms of GGA [PBE-GGA, WC-GGA & PBEsol-GGA] are applied. The mBJ-GGA method including spin-orbital coupling (SOC) & not including SOC was utilised in this investigation and it was carried out in the WIEN2k code. In addition, the TB-mBJ exchange potential analysis classified Sr2ScBiO6 as having a p-type semiconducting nature with an indirect bandgap value of 3.327 eV. Additionally, the mechanical properties analysis and the related elastic constants demonstrate the anisotropic nature of Sr2ScBiO6 with decent mechanical stability. Apart from that, the Sr2ScBiO6 was considered a brittle non-central force solid with dominant covalent bonding. The varying optical parameter evaluations highlighted the potential use of Sr2ScBiO6 in visible-light (vis) and ultraviolet (UV)-based optoelectronic devices. Moreover, the semiconducting nature of Sr2ScBiO6 was verified through its thermoelectric response, which revealed that the charge carriers mostly consist of holes. Over a wide temperature range (100-1200 K), several transport metrics like the Seebeck coefficient (S), electrical conductivity (σ/τ), thermal conductivity (κ/τ), and power factor (PF) are investigated. An optimal value of figure of merit (ZT) ∼ 0.62 at T = 1200 K is accomplished. The extremely lower value of thermal conductivity as well as higher electrical conductivity leads to a higher figure of merit of the investigated system. The Sr2ScBiO6 verified a high ZT value, confirming that the material would be beneficial in renewable energy and thermoelectric (TE) applications.

Theoretical prediction by DFT on properties of β′-SrTa2O6 crystal

Based on the Density Functional Theory (DFT) electronic band structure, state density, linear optics, elastic, dynamic and thermodynamic properties of ??-SrTa2O6 crystal with P4/mbm (No. 127) space group were investigated with the help of ABINIT and Wien2k code. In the study, it was found that the ??-SrTa2O6 crystal is classified as a semiconductor with an indirect bandgap. For this crystal, the dielectric function was obtained and optical constants such as energy loss function, extinction coefficient, absorption coefficient and reflectivity were calculated. The components of the elastic stiffness tensor, the phonon dispersion, the state density and the contribution of each atom to the state density were obtained. Finally, thermodynamic properties were determined for the ??-SrTa2O6 crystal. Furthermore, the changes in free energy (F), internal energy (E), entropy (S) and heat capacity (C) depending on the temperature were investigated.

Investigation of the structural, electronic, mechanical, and optical properties of NaXCl3 (X = Be, Mg) using density functional theory.

In our pursuit of enhancing material performance, our focus is centered on the investigation of sodium-based halide perovskites, specifically NaXCl3 (where X = Be & Mg). We are utilizing first-principles methods based on density functional theory (DFT) to delve into these materials' properties and potential improvements. This investigation is executed using the WIEN2K code, aiming to uncover a deeper understanding of these materials' properties and potential enhancements. In this study, we utilize the Full Potential Linear Augmented Plane Wave (FP-LAPW) approach to analyze the structural, mechanical, electronic, and optical properties of cubic perovskite materials NaXCl3 (X = Be, Mg). We employ the Birch-Murnaghan fitting curve to assess the structural stability of these compounds, and in each case, the compound demonstrates structural stability in its optimal or ground state. The existence of real frequencies serves as confirmation of the phonon stability for both compounds. To determine the elastic characteristics, the IRelast Package is used. This involves calculating the elastic constants, which demonstrates that the compounds have anisotropic, ductile properties and demonstrate mechanical stability. We investigate the electronic properties by analyzing the density of states and the band structure. Both compounds exhibit an indirect band gap energy of 4.15 eV for NaBeCl3 and 4.16 eV for NaMgCl3. We analyze both the total and partial density of states to gain insight into the contributions of different electronic states to the band structure. Furthermore, optical characteristics, including the dielectric function, absorption coefficient, refractive index, and reflectivity, are investigated across an energy spectrum ranging from 0 to 15 eV. These findings can offer a comprehensive insight into the development of advanced electronic devices with improved efficiency and enhanced capabilities. Furthermore, they have the capacity to inspire experimental researchers to delve further into this field for subsequent explorations.

Investigation of the optoelectronic properties of cubic metal halide perovskite compound RbSiCl3

Lead free halide metal perovskite compounds have been exploring more since last decades due to their wide potential applications as well as their environmental friendly nature. Presented work agreements with the density functional investigation of the material properties (optoelectronic) of lead free halide metal perovskite compound RbSiCl3 by using WIEN2k code that is rely on FP-LAPW: full potential-linearized augmented plane wave method. The optoelectronic response are well explored by the Perdew Burke Ernzergof GGA exchange correlation functional. The computed energy band gap of this compound is 0.96 eV and results reveal that it is direct band gap semiconductor material. In addition, the integrated absorption coefficient also computed through absorption spectra, which gives the value 123.39 (×104 eV/cm). All computation proves the utility of the compound for photovoltaic and optoelectronic applications.

First-principles calculations for comparative band structure study of SrTiO3 perovskite on bulk and layered phases for efficient optoelectronic conversion

A computational investigation over structural, electronic, optical, thermal, thermoelectric and elastic properties of the bulk and layered phases of perovskite compound namely SrTiO3 have been computed using WIEN2K code by means of Full-potential (FP) Linearized Augmented Plane Wave (LAPW) method implemented from DFT (Density Functional Theory) by applying Generalized Gradient Approximations (GGA), Local Density Approximations (LDA), modified Becke Johnson (mBJ) and Spin Orbit Coupling (SOC) computations. Further on this study we made surface structure of this compound by creating a supercell with various distances between the layers and compared their properties with bulk SrTiO3. The layered surfaces of SrTiO3 with varying distances are (i) single top layer (ii) double SrTiO3 layers with 5 a.u. distance (iii) double SrTiO3 layers with 18 a.u. distance have been constructed using the Struct editor program implemented in the WIEN2k code. The structural parameters viz., lattice constant, bond length, bond angles, formation energy, the electronic parameters such as band gap, Density of States (DoS), band structure and optical fundamental constants like dielectric function, optical conductivity, refraction, transmittance, absorbance, resistivity, reflectivity, Phonon dispersion curves and thermal properties such as Debye temperature, entropy, Gibbs free optimized energy (stabled / optimized state), thermoelectric properties such as Seebeck coefficient, Power factor, thermoelectric figure of merit, Pugh's ratio, elastic constants, modulus of elasticity and stiffness matrix have been computed and available results are compared and agreed well with the literature. The SrTiO3 bulk and layered surface exhibits direct band gap located at the Γ symmetry point of the Brillouin zone. From all the above analysis the layered materials with optimum variation of distances (double layers with 5 a.u) are predominantly favorable and efficient than bulk SrTiO3 for optoelectronic devices.

Tuning of band gap by variation of halide ions in K2CuSbX6 (X = Cl, Br, I) for solar cells and thermoelectric applications

The double perovskites have obtained remarkable attention in the field of solar cells and renewable energy applications. Here in present article, the optical and transport properties of K2CuSbX6 (X = Cl, Br, I) are illustrated by DFT based simulation WIEN2K codes. The formation energy has been calculated for thermodynamic stability. The indirect band gaps (1.12, 0.80, and 0.43) for (Cl, Br, I) studied DPs halides are reported from band structures which instigate diverse optoelectronic and transport applications. The width of absorption band increases from Cl to I and shifted towards to lower frequency region. Furthermore, thermoelectric parameters are evaluated in the temperature range 200–600K and chemical potential ±0.15 eV. The ultralow values of lattice conductivity and large ZT at 300K increases their significant importance for thermoelectric generators and renewable energy devices.

Structural, electronic, mechanical and phonon properties of half-Heusler GaNiSb, InNiSb and InPdSb alloys via first-principles calculations

In this report, the ground state properties of the half-Heusler GaNiSb, InNiSb and InPdSb alloys in the cubic LiAlSi-type structure, are investigated using the Full Potential Linearized Augmented Plane Wave (FP-LAPW) method as implemented in WIEN2k code, based on Density Functional Theory (DFT). The Perdew–Berke–Ernzerhof (PBE) Generalized Gradient Approximation (GGA) is used for exchange–correlation functional. The calculated formation energies and volume-optimization curves of three different structural configurations (Type 1, Type 2 and Type 3) of these alloys reveal that Type 3 configuration is the most favorable (lowest energy structure) structure. According to the Slater–Pauling rule, the studied alloys are non-magnetic in nature in the stable Type 3 configuration. Therefore, the calculation of ground state properties of these alloys are examined in the Type 3 structural configuration and non-magnetic state. The results of electronic structure and density of states reveal that these alloys are metallic in nature. These alloys are dynamically stable as demonstrated by their calculated phonon dispersion spectra. As the three independent elastic constants C11, C12 and C44 satisfy Born–Huang stability condition, these alloys are stable elastically. The studied alloys are ductile in nature, elastically anisotropic and GaNiSb is found to be stiffer than InNiSb and InPdSb by the calculation of mechanical properties. The present work is in good agreement with the previously reported results.

Investigating structural, electronic, magnetic, and optical properties of Zr doped and Ti-Zr co-doped GaN for optoelectronic applications

Search of new novel materials for bringing advancement in the field of energy storage and optical materials is tremendously growing in order to meet future challenges. Gallium nitride (GaN) shows exceptional optoelectronic behavior which is highly needed for production of optoelectronic devices. Therefore, in this research study, we investigate the structural, electronic, magnetic, and optical properties of pure GaN, titanium doped GaN (Ti@GaN), zirconium doped GaN (Zr@GaN) and Ti-Zr co-doped GaN using the Wien2k code. Proactive role of dopants Ti and Zr d-states is observed which appreciably tune electronic properties. GaN remains non-magnetic after zirconium substitution with Ga atom however, Ti doping and Ti-Zr co-doping produce magnetism into GaN with total magnetic moments of 0.99 and 1.503 respectively. Substitution of Ti/Zr into GaN may be more favorable at N-rich conditions due to lower formation energy. Absorption spectrum of Ti@GaN and Zr@GaN show blueshift while for Ti-Zr@GaN material exhibit redshift. However, absorption spectra of both proposed materials significantly enhanced in the UV region which propose their potential uses in the high power UV optoelectronics, spintronics, photonics devices and in solid state nano-emitters.

Enlightening the stability and optoelectronic properties of Ba2MLnSe5 (M = Ga, In; Ln = Y, Nd, Sm, Gd, Dy, Er) semiconductors: A first-principles study

Emerging materials for optoelectronic and sustainable energy applications include chalcogenide materials. Therefore, using density functional theory and WIEN2k code, we investigated the electrical and optical properties of Ba2MLnSe5 (M ​= ​Ga, In; Ln ​= ​Y, Nd, Sm, Gd, Dy, Er). In GGA ​+ ​U approximation, the band gaps for Ba2MLnSe5 (M ​= ​Ga, In; Ln ​= ​Y, Nd, Sm, Gd, Dy, Er) are calculated to be from 1.95 to 2.31 ​eV. Full geometric optimization was performed on the base of cell parameters. The obtained results indicated the overall semiconducting nature of Ba2MLnSe5 (M ​= ​Ga, In; Ln ​= ​Y, Nd, Sm, Gd, Dy, Er). From the electronic charge density study, we confirmed that the character of the investigated compound is mainly covalent. The top of the valence bands and the bottom of the conduction bands are due to Ba-d orbitals with minor contributions of Ga-p/d, Se-p/d orbitals and M-d (M ​= ​Ga, In; Ln) states. Finally, we predicted the optical properties, such as the dielectric function, optical conductivity, refractive index, extinction coefficient, absorption coefficient, reflectivity coefficient, and loss function for polarized incident radiation with electrical vector E parallel to the crystalline axes a and c. Remote sensing and surgical equipment become more important due to the minimal reflection and maximal absorption of light in the infrared to the visible area. The resulting results are consistent with the experimental and theoretical data that is currently accessible. ‘

An insight into the structural, electronic, magnetic and optical properties of Cs doped and Cs-X (X=Mn, Fe) co-doped CdS for optoelectronic applications

This research presents detailed investigations of the structural, electronic, magnetic and optical properties of cesium doped and Cs-X (X = Mn, Fe) co-doped CdS. We employ Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation within Wien2K code. Cs-X (X = Mn, Fe) co-doped CdS materials exhibit magnetic moment and thus, show magnetic character. Role of 5p-states of Cs atom and 3d-states of Mn, Fe atoms appreciably tune the electronic properties. Optical absorption spectrum of Cs@CdS shows blueshift while Cs–Mn/Fe co-doping into CdS causes redshift. However, the ability of proposed materials to absorb electromagnetic radiations in the 0–7 eV energy range and presence of the magnetism illustrates their potential uses for fabrication of novel optoelectronic and spintronic devices.

Structural, Electronic, Elastic, Mechanical, Optical and Thermoelectric Properties of the Chalcogenide Double Perovskites A2GaNbS6 (A = Ca, Sr and Ba): Insights From Density Functional Theory Calculations

Abstract Recently, the lead-free double perovskite compounds have been evinced to be promising candidate for thermoelectric and optoelectronic technologies. In this paper; we have probed a theoretical works on the different physical properties: Structural, electronic, elastic, optical and thermoelectrical properties of the chalcogenide double perovskites A2GaNbS6 (A=Ca, Sr and Ba) within the instructions of density functional theory. The calculations have incorporated using the full potential linearized augmented plane waves (FP-LAPW) method within gradient generalized approximation (GGA) and the modified Becke-Johnson potential (mBJ) to describe the exchange-correlation potential as embodied in the WIEN2K code. The computed structural results show that the non-magnetic structure state is energetically the most stable structure in the cubic Fm3̄m (225) configuration, also the elastic and mechanical properties indicate that A2GaNbS6 (A=Ca, Sr and Ba) have a ductile nature. According to the electronic plots the three compounds have a semiconducting behavior with indirect (pseudo-direct) band gap of 1.21, 1.28 and 1.32 eV. Important optical responses of studied chalcogenide double perovskites are found in the visible and ultraviolet energy ranges. Finally, the thermoelectric effectiveness of the three compounds have been probed by computing parameters like Seebeck coefficient, electrical conductivity, thermal conductivity and figure of merit with semi-classical Boltzmann theory and constant relaxation time approximation as implemented in BoltzTrap code, the obtained results show that the chalcogenide double perovskites could be a good candidate for thermoelectric applications.

First-principles calculations to investigate structural stability, half-metallic behavior, thermophysical and thermoelectric properties of Co2YAl (Y = Mo, Tc) full Heusler compounds

The present manuscript reports structural stability, half-metallic behavior, thermophysical and thermoelectric properties of Co2MoAl and Co2TcAl full Heusler compounds using first-principle calculations. The full-potential linearized augmented plane wave method within the framework of density functional theory is implemented and WIEN2k code is incorporated in the stable Fm-3 m phase to attain the desired results. The L21 phase is found as the most stable phase for both compounds. The optimized equilibrium lattice parameters in the stable phase are 5.89 Å, 5.86 Å for Co2MoAl and Co2TcAl respectively. The electronic band structure study proves that both compounds Co2MoAl and Co2TcAl have indirect band gaps of 0.74 eV and 0.85 eV respectively in majority spin alignment. The half-metallic performance of the present set of compounds is explained by the spin-resolved density of states. The Fermi level at the Brillouin zone point approves the metallic as well as semiconducting behavior. To elucidate the thermodynamical stability of these materials against pressure and temperature by implementing the quasi-harmonic approximation of various parameters like Debye temperature, Gruneisen parameters and specific heat are studied successfully. To know the thermoelectric response, Seebeck coefficient and electrical conductivity are computed using the BoltzTrap code. The thermodynamic profile delivers that the present set of compounds possesses no anomalies with respect to the phase transition or instabilities. The computational study insights that the compounds can be synthesized experimentally and find a route towards spintronic and thermoelectric applicability.