Calculated Formation Energies Research Articles

Cu - Nitrogen doped graphene (Cu–N/Gr) nanocomposite as cathode catalyst in fuel cells – DFT study

Novel Cu-nitrogen doped graphene nanocomposite catalysts are developed to investigate the Cu-nitrogen doped fuel cell cathode catalyst. Density functional theory calculations are performed using Gaussian 09w software to study the oxygen reduction reaction (ORR) on Cu-nitrogen doped graphene nanocomposite cathode catalyst in low-temperature fuel cells. Three different nanocomposite structures Cu2–N6/Gr, Cu2–N8/Gr and Cu–N4/Gr were considered in the acidic medium under standard conditions (298.15 K, 1 atm) in order to explore the properties of the fuel cell. The results showed that all structures are stable at the potential range 0–5.87 V. Formation energy, Mulliken charge and HOMO-LUMO energy calculations showed that Cu2–N6/Gr and Cu2–N8/Gr are more stable structure-wise, while free energy calculations showed that only Cu2–N8/Gr and Cu–N4/Gr structures support spontaneous ORR. The maximum cell potential under standard conditions was shown at 0.28 V and 0.49 V for Cu2–N8/Gr and Cu–N4/Gr respectively. From the calculations, the Cu2–N6/Gr and Cu2–N8/Gr structures are less favorable in H2O2 generation; however, Cu–N4/Gr showed the potential for H2O2 generation. In conclusion, Cu2–N8/Gr and Cu–N4/Gr are more favorable to ORR than Cu2–N6/Gr.

Investigation of the effect of oxygen vacancies on the electronic properties of lizardite

Doping and chemical substitutions of clay minerals have been very successful recently in the design of new novel materials. The serpentine mineral, lizardite has attracted a lot of attention due to its abundance in nature across the world and its eco-friendly behavior. A detailed study of lizardite has been performed to understand the effects of the presence of vacancies placed strategically at three positions of the structure, thereby leading to six different configurations. Formation energy calculations exhibit the possibility of obtaining all the conformations considered in this work. Moreover, free energy calculations demonstrate the stability at higher temperatures. The presence of the oxygen vacancies in the site that binds the Si atoms and also that between the Si atom and the Mg atom decreases the gap. However, the oxygen vacancy on top of the tetrahedral layer of the clay mineral induces an insulator-metal transition. Energy-bands and the density of states display the modified electronic properties of the system with vacancies. Lowdin-charge analysis and the isolines of the charge distribution in different planes provide information on the modifications brought about by the vacancies. Hence, vacancies have a vital role in controlling the band-gap. Moreover, the modifications of the other electronic properties could provide a promising route towards to achieving valuable thermoelectric materials.

Electronic structure and optical properties of tin (IV) doped transparent perovskite crystal BaTiO3 for efficient visible optoelectronic devices and solar cells

The electronic structure and optical properties of BaSnxTi1−xO3 (BSnT, 0 ≤ x ≤ 0.375) perovskite crystals have been investigated using the newly developed PBEsol and nKTBmBJ approaches within the full potential linear augmented plane wave (FPLAPW) method for potential applications in optoelectronics. The lattice parameter showed a0 a quasi-linear increase with Sn content (with a bowing parameter of ∼ 0.048 Å). The calculated formation energy indicates that BSnT crystals are thermodynamically stable. BSnT exhibits a direct bandgap within the Sn composition range of ∼ 0.03–0.375, which can cover the emission wavelengths within the UV–visible spectrum region of ∼ 375–442 nm. The addition of Sn dopants into BaTiO3 results in a significant increase in the bandgap (by ∼ 496 meV, up to x = 0.375) due to the resonant interaction between O_2p orbitals and Sn_4d states in the upper valence band. Furthermore, the dielectric functions (ε1, ε2), refractive index n, extinction coefficient k, reflectivity R, and absorption coefficient α were determined for the radiation range of 0–12 eV and were found to be in close agreement with experimental spectra. BSnT exhibits good absorption within the ultraviolet spectrum while remaining transparent within the visible spectrum. Sn-doped BaTiO3 holds great promise as a transparent and/or active layer in the development of modern/low-cost solar cells and light-emitting diodes (LEDs) for visible light communication (VLC).

Unraveling the structural and mechanical stability, electronic, and optical properties of (LaxSr1-xVO3)n (n =1, 2; x = 0, 0.5, 1)

We have investigated the structural, chemical, and mechanical stabilities, electronic structures, and optical characteristics of (LaxSr1-xVO3)n ( where, n =1,2; x = 0, 0.5, 1) systems using the ab-initio calculations. The negative values obtained from formation and cohesive energy calculations, modulus of elasticities, Poisson’s and Pugh’s ratios, anisotropy factor, and Cauchy pressure indicate that these materials have excellent structural and mechanical stability, which can be synthesized experimentally. Furthermore, the Mott-Hubbard metal-insulator transition (MIT) is investigated using the maximum entropy model (MEM) from the data obtained from dynamical mean field theory (DMFT). From the calculation, MIT are observed for pristine LaVO3 and SrVO3 at U = 4.5 eV with β = 8.0 (eV )−1 and U = 2.5 eV with β = 6.0 (eV )−1, and the MIT parameters for LaSrV2O6 system are observed at U = 4.0 eV with β = 10.0 (eV )−1 respectively. The photo-induced behaviors of these materials have also been investigated using the dielectric function, index of refraction, Eloss function, absorptivity, and optical conductivity in the IR-to-UV regions, including the visible spectrum.

Mechanocatalysis: Simple and Rapid Mechanochemical Synthesis of Ammonia in Hydrogen, Nitrogen, and Water System

AbstractMechanical force‐induced N2 fixation is an emerging strategy for single‐step ammonia synthesis under room temperature and atmospheric pressure. Here, we demonstrate a simple and rapid approach to synthesize NH3 in the N2+H2+H2O system and illustrate the reaction mechanism by theoretical calculations. The NH3 generation rate can reach 2.847 mg L−1 h−1 with an NH4+ selectivity of 99.45 wt.%. The presence of H2 can inhibit oxidation reactions to form NO3− by‐products and promote proton generation from H2O dissociation. The calculated formation energy of H‐adatom and OH‐adatom from H2O cleavage is −2.86 eV in N2+H2+H2O system, much lower than that in N2+H2O system, verifying much easier dissociation of H2O molecules and significantly facilitated proton generation to enlarge the NH4+ yield. This work provides a simple approach to improve mechanochemical N2 fixation performance and highlights a proton generation enhancement mechanism.

Electronic and optical properties of Na, Mg, and Al substituted Zinc-oxide Nanotube: An insight DFT study

Background: The present work deals with DFT-based theoretical investigations on pristine and metal (M = Na, Mg, and Al) substituted zinc oxide nanotube (M-ZnONT). The investigation advocates a change in the electronic bandgap of ZnONT on the respective substitution of Zn with Na, Mg, and Al. The forbidden energy gap vanishes on Na incorporation, while Al substitution brings the gap to 0.08eV. The formation energy calculations suggest the feasibility of these metallic substitutions, of which Na incorporation is most favorable. Partial density of state (PDOS) analysis is well correlated with band structures. A localized state above the Fermi level contributed from Al-3p in Al-ZnONT suggests the electronic affinity of Al-ZnONT for incoming nucleophiles. Our optical investigation shows large ε1(ω) values in far-infrared (IR) and visible (Vis) regions for M-ZnONT. Hence, suggests a high refractive index for the metal-substituted ZnONTs in the prescribed range. The study suggests that photonic energy loss due to attenuation, bending, and absorption are weak in ultra-violet (UV) and far UV regions i.e, (3eV to 8eV). However, for the respective energy range, high reflectivity is predicted. This indicates the nanotubes as a good reflector for the purpose of coating material surfaces where high reflection is demanded. Objective: Finding electronic and optical properties of functionalized ZnONT using DFT method. Methods: All calculations have been performed in the framework of density functional theory (DFT) using Troullier Martins’s norm-conserving pseudo-potential. Results: Metal incorporation at the surface of ZnONT consequent intense ε1(ω) values in far infra-red and visible regions for M-ZnONT. Conclusion: The investigation suggests that the metal-substituted nanotube is a good reflector for coating material surfaces where high reflection is demanded.

Insight into the structural, electronic, optical, and elastic properties of niobium carbide

ABSTRACT The structural parameters, electronic, optical, and elastic properties of Niobium Carbide (NbC) compound within four different structures: rock-salt (RS), wurtzite (WZ), cesium chloride (CsCl), and Nickel Arsenide (NiAs) are examined using the Full-Potential Linearized-Augmented Plane Wave (FP-LAPW). The exchange–correlation potential (VXC) has been treated by Perdew, Burke, and Ernzerhof's generalized gradient approximation (PBE-GGA) when structural properties, transition pressure, and elastic properties are estimated. For electronic properties, in addition to (PBE-GGA), the modified Becke–Johnson (mBJ-GGA) was used for increased accuracy. Present results show that the RS of NbC is the most stable among the four examined structures with the lowest equilibrium energy. The calculated lattice constants are in good agreement with the former calculations. The elasticity and the formation energy calculations show that NbC is stable within the four studied structures. The electronic band structure calculations of NbC show that it has a metallic nature in the four considered structures.

Insights to the fracture toughness, damage tolerance, electronic structure, and magnetic properties of carbides M2C (M = Fe, Cr)

The fracture toughness, damage tolerance, electronic structure, and magnetic properties of M2C (M = Fe, Cr) carbides were analyzed using first-principles calculations. Calculations of formation energy and modulus of elasticity indicate that a Cr/Fe ratio of 1/3 is a critical threshold which triggers a significant increase in the corresponding stability and related mechanical properties. Cr atomic content enhances the crack resistance, while Cr has a significantly detrimental effect on damage resistance. The electronic properties demonstrated that the Cr atom content enhances the metallic, ionic and covalent bonding. Furthermore, the reduction in the coordination number of Fe atoms is the main reason for the reduction in the local magnetic moment of the low-spin Cr atoms, which is strongly supported by the electronic structure. These studies provide detailed insights into Cr-containing carbides, providing valuable theoretical and technological information for the knowledge-based design and prediction of the mechanical properties of chromium-containing iron-based materials.

Diffusion of Sn donors in β-Ga2O3

Diffusion of the n-type dopant Sn in β-Ga2O3 is studied using secondary-ion mass spectrometry combined with hybrid functional calculations. The diffusion of Sn from a Sn-doped bulk substrate with surface orientation (001) into an epitaxial layer is observed after heat treatments in the temperature range of 1050–1250 °C. Calculated formation energies of Sn-related and intrinsic defects show that the migration of Sn is mediated by Ga vacancies (VGa) through the formation and dissociation of intermittent mobile VGaSnGa complexes. The evolution of the Sn concentration vs depth profiles after heat treatments can be well described by a reaction–diffusion model. Using model parameters guided by the hybrid functional calculations, we extract a VGaSnGa complex migration barrier of 3.0 ± 0.4 eV with a diffusion coefficient of 2 × 10−1 cm2/s. The extracted migration barrier is consistent with our theoretical predictions using the nudged elastic band method, which shows migration barriers of 3.42, 3.15, and 3.37 eV for the [100], [010], and [001] directions, respectively.

Efficient predictions of formation energies and convex hulls from density functional tight binding calculations

• DFTB was interfaced with CASM to enable efficient calculations of formation energies • Efficiency and accuracy of DFTB vs. DFT was carried out for SiC and ZnO materials • DFTB can be an order of magnitude faster than DFT for predicting formation energies Defects in materials significantly alter their electronic and structural properties, which affect the performance of electronic devices, structural alloys, and functional materials. However, calculating all the possible defects in complex materials with conventional Density Functional Theory (DFT) can be computationally prohibitive. To enhance the efficiency of these calculations, we interfaced Density Functional Tight Binding (DFTB) with the Clusters Approach to Statistical Mechanics (CASM) software package for the first time to calculate formation energies and convex hulls. Using SiC and ZnO as representative examples, we show that DFTB gives accurate results and can be used as an efficient computational approach for calculating and pre-screening formation energies/convex hulls. Our DFTB+CASM implementation allows for an efficient exploration (up to an order of magnitude faster than DFT) of formation energies and convex hulls, which researchers can use to probe other complex systems.

Discerning the crystal structure and engineering the optoelectronic properties through substitution of divalent cations (M= Zn, N = Ge) in C3H3MxN1-xI3 for solar cell applications

Herein, we identified the ground state crystal structures of C3H3ZnxGe1-xI3 hybrid perovskite materials and investigated their optoelectronic properties for the first time using van der Waals correction, included ab initio calculations with hybrid functionals. The energy difference and formation energy calculations are done to perceive the information related to their structural phase transition and stability. Chemical bonding between the atomic constituents are found from charge density distribution, projected crystal orbital Hamiltonian population (pCOHP) and its integration (IpCOHP) results. Our electronic structure calculations predict the compositions with x = 0, 0.25, 0.5, 0.833 as indirect band gap materials and x = 0.667 and 1 as direct band gap materials. Our results also predict that the composition with x = 0.833 value belongs to the classification of intermediate band gap semiconductor. The effective mass of holes and electrons are calculated at valence and conduction band edges, respectively, to realize the transport property of carriers. The absorption coefficient calculations infer that composition with x = 0.667 shows better optical absorption property in the visible region compared to other compositions. The applicability of these materials towards solar cell device performance is explored by calculations of cell parameters and it is found that the power conversion efficiency is higher for the composition with higher Ge concentration than Zn. Specifically, low PCE values in the range of 8.66–17.32% corresponds to C3H3Zn0.833Ge0.167I3 and high PCE values in the range of 16.52–33.04% corresponds to C3H3Zn0.5Ge0.5I3.

Cd implantation in α−MoO3 : An atomic scale study

Lamellar $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{MoO}}_{3}$ crystals were implanted with low fluence of radioactive $^{111\mathrm{m}}\mathrm{Cd}$ ions at ISOLDE-CERN. Subsequently, we have probed the interaction of the Cd impurity in the lattice with native point defects, such as oxygen vacancies, as a function of annealing temperature using the time differential perturbed angular correlations nanoscopic technique. The experimental data were complemented and interpreted by modeling different Cd-defect configurations in $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{MoO}}_{3}$ with first-principles density functional theory (DFT). The agreement between experiments and DFT simulations shows that only the interstitial Cd (${\mathrm{Cd}}_{I}$) prevails in the van der Waals gap, by inducing a polaron effect. Upon raising the annealing temperature, ${\mathrm{Cd}}_{I}$ is able to trap hole charge carriers resultant from the oxygen vacancies ${V}_{\mathrm{O}}$. Oxygen vacancies were found to form most commonly at two-fold coordinated (O2) atoms. According to comparison DFT results with the experimental electric field gradient values (${V}_{zz}$ and $\ensuremath{\eta}$) and the calculated formation energies for different defect complexes, the configuration of ${\mathrm{Cd}}_{I}$ with two (O2) vacancies (${V}_{\mathrm{O}2}$), located at different planes, is found to be more favorable and stable than the other defect configurations. The electron-polaron formation around the Cd impurity at an interstitial site is enhanced by inducing (O2) vacancies with the creation of hole polaron states.

Two-dimensional PtI2/Bi2S3 and PtI2/Bi2Se3 heterostructures with high solar-to-hydrogen efficiency

The PtI2/Bi2S3 and PtI2/Bi2Se3 heterostructures driven Z-schemes are found for photocatalytic hydrogen/oxygen evolution reaction (HER/OER) accompanied by a high effect solar-to-hydrogen efficiency (η′STH). Three preferable heterostructures are recognized from possibly stacking modes using the PtI2 and Bi2X3 (X = S, Se, Te) monolayers, according to the calculated formation energies. The obtained band alignments and built-in fields justify that the PtI2/Bi2S3 and PtI2/Bi2Se3 heterostructures support the Z-scheme for the photocatalytic HER and OER, but the PtI2/Bi2Te3 one fails to match the potential prerequisite. The solar-to-hydrogen efficiency η′STH are evaluated according to the overpotentials and bandgaps of the monolayers. The results indicate that the η′STH of 16.36% and 18.23% can be achieved for the two heterostructures and are substantially higher than that of 9.60% for the PtI2 monolayer, although the Bi2S3 and Bi2Se3 monolayers fail to drive HER by themselves. The strain engineering demonstrates a remarkable impacting effect on efficiency and can induce the maximum η′STHs of 24.77% and 22.48% under biaxial strains of − 2% and + 8% for the PtI2/Bi2S3 and PtI2/Bi2Se3 heterostructures, respectively. Moreover, the alterations in the Gibbs free energies indicate both HERs and OERs are feasible in thermodynamics. Therefore, the newfound PtI2/Bi2S3 and PtI2/Bi2Se3 heterostructures may be used as candidates for developing HER photocatalyst.

Enhancing quantum capacitance of iron sulfide supercapacitor through defect-engineering: A first-principles calculation

Quantum capacitance (CQ) has recently emerged as a solution for the saturated growth of supercapacitor performances. The CQ depends on the density of states of the electrode materials, which could be tuned by several approaches (i.e., introducing dopants). In this case, a transition metal sulfide material with a narrow band gap, such as hexagonal iron sulfide (h-FeS), has enormous advantages. In this study, we predict p-type defect importance in the h-FeS structure on capacitance enhancement through the quantum capacitance mechanism. From the first-principle calculation, the Cr-doped h-FeS (FeS:Cr) anode results in integrated quantum capacitance (CQint) of 1043 F/g, or 27 times more than pristine h-FeS. From the formation energy calculation, the Cr-doped structure has a lot of stable charged states enabling additional redox-related capacitance. As dopant concentration increased, the CQint is found to increase but then saturate due to delocalized state appearances. These findings imply that a first-principles understanding is essential to predict the enhanced capacitance properties on h-FeS and TMS supercapacitors.

First principles calculations of electronic and optical properties of InSe nanosheets doped with noble metal atoms

Monolayer Indium Selenide (ML-InSe) is studied for 4x4 supercell structure through ab initio calculations. The electronic and optical properties of ML-InSe for both pristine and substitutional doped ML-InSe with Palladium (Pd), Platinum (Pt), Silver (Ag), and Gold (Au) atoms have been calculated. With substitutional doping, ML-InSe has been observed to have a spin-dependent electronic structure. The flat energy bands near the Fermi level are observed in ML-InSe with doping elements placed in In site. The flat bands of d orbitals of some noble metal atoms are formed by the projected density of states (PDOS). The PDOS calculations show that the s-orbital of In and p-orbital of Se form the conduction band edge. The energetically favorable position of doping atoms is found to be the PtIn substitution atom according to formation energy calculations. For each studied structure, the bond length of the first neighbor of doping atoms in doped ML-InSe, static dielectric constant (ε0), refractive index, and energy band gap have been calculated. In the structure ML-InSe with AuSe, ε0 reaches ∼ 8.15. Another important result is that substitutional doping induces some peaks in the lower energy region of the imaginary part of the dielectric function. These peaks mainly refer to the absorption in related regions and may be important for the optoelectronic properties of ML-InSe.

Site-specific atomic substitution in a giant magnetocaloric Fe2P -type system

Giant magnetocaloric (GMC) materials constitute a requirement for near room temperature magnetic refrigeration. (Fe,Mn)$_2$(P,Si) is a GMC compound with strong magnetoelastic coupling. The main hindrance towards application of this material is a comparably large temperature hysteresis, which can be reduced by metal site substitution with a nonmagnetic element. However, the (Fe,Mn)$_2$(P,Si) compound has two equally populated metal sites, the tetrahedrally coordinated $3f$ and the pyramidally coordinated $3g$ sites. The magnetic and magnetocaloric properties of such compounds are highly sensitive to the site specific occupancy of the magnetic atoms. Here we have attempted to study separately the effect of $3f$ and $3g$ site substitution with equal amounts of vanadium. Using formation energy calculations, the site preference of vanadium and its influence on the magnetic phase formation are described. A large difference in the isothermal entropy change (as high as 44\%) with substitution in the $3f$ and $3g$ sites is observed. The role of the lattice parameter change with temperature and the strength of the magnetoelastic coupling on the magnetic properties are highlighted.

Graphene-Supported Tin Single-Atom Catalysts for CO2 Hydrogenation to HCOOH: A Theoretical Investigation of Performance under Different N Coordination Numbers

The effects of the adjustment of the N coordination number in Sn single-atom catalysts toward the activity and selectivity of CO2 hydrogenation to HCOOH are systematically explored via density functional theory calculations. The stability of the studied catalysts was evaluated by formation energy calculations, and the calculated results indicated that Sn-NxC4–x-G (x = 1–4) are structurally stable. Through the discussion of the reaction mechanism, the optimal path of CO2 hydrogenation to HCOOH on all the studied catalysts is via CO2* + H2* → HCOO* + H* → HCOOH*. In addition, they have different speed limit steps. For Sn-N1C3-G and Sn-N2C2-G, the rate-determining step of CO2 to HCOOH is CO2* + H2* → HCOO* + H*, while the rate-determining step of the other two catalysts is HCOO* + H* → HCOOH*. Meanwhile, the order of catalytic activities of Sn-NxC4–x-G is determined to be Sn-N1C3-G > Sn-N2C2-G > Sn-N3C1-G > Sn-N4-G. Furthermore, the origin of the catalytic activities for HCOOH synthesis on Sn-NxC4–x-G is revealed through the calculated p-band center. It demonstrated that the p-band center of the Sn atom is a good descriptor to evaluate the catalytic activity for HCOOH synthesis in the Sn-NxC4–x-G system.

Thermodynamics and a definite large half-metallic spin gap along with a magnetic anisotropy in La-doped Ba[formula omitted]NiIrO[formula omitted

Electron doping (i. e., by replacing Ba+2 with La+3) impact on the electronic and magnetic properties of Ba2NiIrO6 system is investigated using ab-initio calculations with the inclusion of Hubbard parameter U along with spin–orbit coupling effects. The calculated formation energies affirm the experimental realization of all motifs at ambient conditions. Whereas, the elastic properties confirm the mechanical stability, ductility, and thermal conductivity of all the structures. It is revealed that anti-ferromagnetic/ferromagnetic (FM) interaction between Ni and Ir ions are energetically stable in pristine motif having an energy band gap (Eg) of 0.70/0.35 eV using the GGA+U method without/with the inclusion of SOC effects, which is in good agreement with the recent experimental results (Feng et al., 2021). Interestingly, La-doped structures depict the half-metallic FM behavior except for 50% concentration, which results in conductivity of the spin-minority channel owing to the admixture of Ir 5d states. On the other hand, the spin-majority channels exhibit an insulating nature having a large Eg of 2.53/2.63/2.49 eV for 12.5%/25%/37.5%, which looks sufficient to restrict the spin reversal and assure high spin filtering efficiency. Moreover, La-doping leads to the existence of mixed-valence state of ＋6/＋5 having a configuration 5d3 (t2g3↑t2g0↓eg0↑eg0↓)/5d4 (t2g3↑t2g1↓eg0↑eg0↓) for Ir ion. Finally, a reasonable magneto-crystalline anisotropic constant of ∼×106 erg/cm3 in all La-doped Ba2NiIrO6 systems is predicted, which is a good signal for their potential utilization in data storage devices.

Thermodynamics evaluation of half-metallic ferromagnetism in N-doped XTiO3 (X = Ca, Sr, and Ba) systems: DFT calculations

Half-metallic (HM) materials with high magnetic transition temperature (TC) combined with a wide energy gap (Eg) in insulating spin channel are desired for the realization of modern spin based devices due to their stable ferromagnetic (FM) ordering, spin-filtering, and high mean free path. Herein, the formation energetics, electronic, and magnetic characteristics of N-doped XTiO3 (XTO) (X = Ca, Sr, and Ba) perovskite oxides (PO) were inspected by first-principles calculations, where one of the oxygen (O) atom is replaced by nitrogen (N) atom. The calculated formation energy and elastic constants values confirm the thermodynamical as well as elastic stability of all doped systems. Our calculations show that all undoped PO systems display a non-magnetic insulating behavior. On the other hand, all doped motifs show magnetic character with an integral induced magnetic moment of 1.00 μB. Further, it has also been observed that magnetism in all these doped systems mainly originates from p orbitals of the dopant N. Interestingly, all doped systems have 100% spin splitting at Fermi level depicting a HM FM behavior with large Eg of 1.61, 1.65, and 1.59 eV in spin minority channels for XTO (X = Ca, Sr, and Ba) systems, respectively. Further, a long range stable FM ordering with TC > RT is predicted in these doped materials by computing the magnetic energy solutions for FM and anti-ferromagnetic (AFM) ordering at various distances between two N atoms. The current study suggests that doping strategy with non-magnetic dopant in different PO materials could be a useful approach to modulate the physical features and make them effective for emerging spintronic devices operating above RT.

Topologically nontrivial phase in Na2CuX (X= As, Sb, Sn and Bi) full Heusler compounds: Insights from DFT-based computer simulation

The inspection of materials supporting topological excitations is one of the prospective areas of condensed matter physics. This paper is devoted to studying the possibility of the existence of topological phases in Na2CuX (X= As, Sb, Sn and Bi) full Heusler compounds using the FP-LMTO (Full-Potential Linear Muffin-Tin Orbital) method with and without spin-orbit coupling (SOC). The study of structural properties has found that these materials are energetically stable in the Hg2CuTi type structure. Also, formation energy calculations have shown that these materials are convenient to manufacture. Otherwise, band structure calculations show that these materials exhibit the behavior of non-trivial topological materials with a semi-metallic nature. The obtained results in this study, generally, showed that SOC is not a primary cause of the band inversion mechanism.