Full-potential Linear Muffin-tin Orbital Method Research Articles

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.

Electronic structure of short-period ZnSe/ZnTe superlattices based on DFT calculations

In the present study we discuss the effect of variation in the number of monolayers n on the electronic and optical properties of superlattices (SLs) (ZnSe)n/(ZnTe)n. The total energies were calculated by the full-potential linear muffin-tin orbital (FP-LMTO) method, and the exchange-correlation energy was applied in the local density approximation (LDA). First, the calculations show a decrease in the derivative of bulk modulus and electronic bandgap with an increase in the number of monolayers n. Second, the radiation energies up to 15 eV, the dielectric function ε(ω), the refractive index n(ω), and the reflectivity R(ω) are studied. These calculations may be beneficial to understand the properties of short-period superlattices (ZnSe)n/(ZnTe)n.

A Theoretical Analysis of Physical Properties and Half-Metallic Stability under Pressure Effect of the ScNiCrZ (Z=Ga, Al, In) Heusler Alloys

The aim purpose of this study is to investigate the structural, elastic, magnetic, electronic properties and half-metallic stability under pressure of ScNiCrZ ([Formula: see text], Ga and In) quaternary Heusler alloys using full-potential linear muffin-tin orbital (FP-LMTO) method within the gradient generalized approximation (GGA) for exchange, and correlation potential. In order to evaluate the stability of our compounds, the formation energy, and elastic constants have been evaluated. The results showed that our compounds have ferromagnetic ground states and are energetically more stable in type-[Formula: see text] configuration. True half-metallic ferromagnetic behavior with 100% spin polarization at Fermi level [Formula: see text] with high Curie temperature [Formula: see text], and very interesting bandgap in the minority spin are obtained for the three alloys. The calculated total magnetic moment [Formula: see text] for all three alloys is consistent with Slater[Formula: see text]Pauling rule. The half-metallicity is maintained over a wide range of lattice constants making these alloys promising for spintronic, and magneto-electronics applications.

A first-principles investigation of band inversion in topologically nontrivial Na2AgX (X= As, Sb and Bi) full Heusler compounds

Topological nontrivial nature are the latest phases to be discovered in condensed matter physics with insulating bulk band gaps and topologically protected metallic surface states; they are one of the current hot topics because of their unique properties and potential applications. In this paper, we have highlighted a first-principles study of the structural stability and electronic behavior of the Na2AgX (X = As, Sb and Bi) full Heusler compounds, using the Full-Potential Linear Muffin-Tin Orbital (FP-LMTO) method. We have originated that the Hg2CuTi structure is appropriate in all studied materials. The negative values of the calculated formation energies mean that these compounds are energetically stable. The band structure is studied for the two cases relating the existence and the absence of spin-orbital couplings, where all materials are shown to be topologically non-trivial compounds. Spin orbital couplings were noticed to have no significant effect on the electronic properties such as the topological order.

Structural, electronic, elastic, magnetic and thermodynamic properties of Mn2LuZ (Z = B, Al, Ga and In) Heusler compounds: A first‐principle study

AbstractThe study of the structural, electronic, thermodynamic, elastic and magnetic properties of rare‐earth based full Heusler alloys Mn2LuZ (Z = B, Al, Ga and In) have been carried out using the full‐potential linearized muffin‐tin orbital method (FP‐LMTO), within density functional theory (DFT) and generalized gradient approximation (GGA) for exchange and correlation energy. The electronic properties studied have shown that the compounds have a metallic behavior. We have also computed the mechanical properties where we found these full Heusler compounds are mechanically stable. Using the quasi‐harmonic Debye model, the variations of bulk modulus, thermal expansion coefficient, heat capacities, Debye temperature and Gibbs free energy with pressures covering the 0–40 GPa interval and temperatures ranging from 0 to 1500 K were also investigated and in‐depth discussed. The calculated properties represent a solid prediction for the Mn2LuZ (Z = B, Al, Ga and In) Heusler compounds and are awaiting for experimental concretization.

Ab initio calculations of the phase diagrams of tin and lead under pressures up to a few TPa

The paper studies relative structural stability for various crystal phases of tin and lead from first principles with the full-potential all-electron full-potential all-electron linear muffin-tin orbital method to pressures of a few TPa both at zero temperature and at T > 0. Using data from our calculations we construct phase diagrams for the two metals in the region of very high compressions and obtain their melting curves. For tin at pressures <100 GPa and zero temperature, we did not find the region of stability of the body-centered orthorhombic (bco) phase, as it was earlier observed in experiments by Salamat et al [2013 Phys. Rev. B 88 104104]. Our calculations suggest that one structural transition from the tetragonal to cubic phase, bct → bcc, occurs in perfect Sn crystal at T = 0 K in the pressure range of about 27–32 GPa. But any deviation from perfection may cause an orthorhombic distortion of its tetragonal phase. At pressures above 100 GPa, the bcc → hexagonal close-packed (hcp) transition exists in both metals, and the phase boundary has a domed shape and does not rise in temperature above 2 kK. This behavior of the phase boundary with the increasing temperature is caused by the softer phonon modes of the bcc structure and the smaller contribution of lattice vibrations to the free energy of the crystal compared to the hcp phase. At pressures above 2.5 TPa and T ≲ 1 kK, lead can also undergo another structural transition, hcp → fcc, but at T > 1.5 kK there must exist the more energetically preferable bcc → fcc transition.

Insight View of Topological Nontrivial Nature in the Novel Alkali Metal–Based Quaternary Heusler Compounds via Ab Initio Calculations

In this paper, we have highlighted a first-principles study of the structural stability and electronic behavior of the novel alkali metal–based quaternary Heusler compounds (LiNaCuAs, LiKCuAs, NaKCuAs, LiRbCuAs, NaRbCuAs, and KRbCuAs), using the full-potential linear muffin-tin orbital (FP-LMTO) method. The obtained results show that our compounds are energetically more stable in the Hg2CuTi-type structure. The calculated electronic properties with and without spin-orbit coupling (SOC) effects indicate that the majority of compounds naturally present a band inversion order which confirmed the topological nontrivial behavior of these materials. In addition, our results show that SOC is not a primary cause of the band inversion mechanism. The obtained values of the calculated formation energy confirm the physical stability of these compounds against decomposition, and they can be passed in fabrication level.

First-principles calculations to investigate structural, electronic and optical properties of (AlSb)m/(GaSb)n superlattices

Abstract The structural, electronic and optical properties of (AlSb)m/(GaSb)n (m-n: 1-1, 2-2, 1-3 and 3-1) superlattices are investigated within the density functional theory (DFT) by using the last version of the first principles full potential linear muffin tin orbital method (FP-LMTO) as implemented in LmtART 7.0 code. The exchange and correlation potential is treated by the local density approximation (LDA) for the total energy calculations. Our calculations of the band structure show that the superlattices (n ≠ 1) have a direct band gap Γ-Γ. The optical constants, including the dielectric function ϵ(w), the refractive index n(w) and the reflectivity R(w) are calculated and discussed.

First Principle Investigation on the Magnetism of Zinc Blende Structures of 3d (Cr, V, Mn, Cu, Sc)-Doped CdS

Our aim in this paper is to study the influence of doping with transition metals (TM) on the physical properties of CdS. Thus, the structure stability, half-metallic ferromagnetic, and electronic properties of Cr-, V-, Mn-, Cu-, and Sc-doped CdS, at x = 0.0625 concentration have been investigated using first principle calculations based on the density functional theory (DFT). The all-electron full-potential linear Muffin-Tin orbital (FP-LMTO) method and the generalized gradient approximation (GGA) have been employed. The electronic properties indicate that the Cd0.9375Cu0.0625S and Cd0.9375Sc0.0625S compounds are magnetic degenerate semiconductors and the Cd0.9375Mn0.0625S compound is p-type magnetic semiconductor, while the Cd0.9375Cr0.0625S and Cd0.9375V0.0625S compounds are half-metallic ferromagnets. We have also found that the TM-3d states are responsible for the spin-polarization and the induction of magnetic moments in these compounds. Additionally, to explain the origin of half-metallic ferromagnetism, we have calculated the exchange splitting energy Δx(pd) and the exchange constants N0α and N0β. The calculated values suggest that the Cd0.9375Cr0.0625S and Cd0.9375VV0.0625S compounds may be useful for the development of spintronic devices.

First-principles calculations to investigate structural and thermodynamic properties of Ni2LaZ (Z = As, Sb and Bi) Heusler alloys

Structural, electronic, elastic and thermodynamic properties of Ni2LaZ (Z = As, Sb and Bi) Heusler alloys based on rare earth element have been investigated using full-potential linear muffin-tin orbital (FP-LMTO) method within generalized gradient approximation (GGA) in the frame of density functional theory (DFT). By using total energy variations, the independent elastic constants and their pressure dependence have been determined. Also, anisotropic parameter (A), shear modulus (G), Young modulus (E), Poisson’s ratio (ν), ratio (B/G) are calculated. Using quasi-harmonic Debye model, thermodynamic properties of Ni2LaZ (Z = As, Sb and Bi) Heusler alloys are investigated in temperature range 0–1200 K and pressure range 0–50 GPa. The temperature and pressure effects on the unit cell volume, bulk modulus (B), heat capacities (Cv) at stable volume, (Cp), Debye temperatures (θD), Gibbs energies (G), thermal expansion coefficients (α) and entropies (S) are determined from non-equilibrium Gibbs functions. This study allows to understand deeply the structural and thermodynamic properties of Ni2LaZ (Z = As, Sb and Bi) Heusler alloys in shortest time and cost-effective.

First-principles investigation of the structural, elastic, electronic, and optical properties of semiconducting AgBr1–xIx (0 ≤ x ≤ 1) ternary alloys in rock-salt and zinc blende structures

In this work, first principle calculations of the structural, electronic, elastic, and optical properties of novel AgBr1–xIx ternary alloys in rock-salt (B1) and zinc-blende (B3) structures are presented. The calculations were performed using the full-potential linear muffin-tin orbital (FP-LMTO) method within the framework of the density functional theory (DFT). The exchange and correlation potentials were treated according to the local density approximation (LDA). The lattice constants for the B1 and B3 phases versus iodide concentration (x) were found to deviate slightly from the linear relationship of Vegard’s law. The calculated electronic properties showed that AgBr1–xIx alloys in the B3 structure have a direct band gap (Γ – Γ) for all concentrations of x, which means that they can be used in long-wavelength optoelectronic applications, while in the B1 structure they have an indirect (Γ – R) band gap. The elastic constants Cij, shear modulus G, Young’s modulus E, Poisson’s ratio ν, index of ductility B/G, sound velocities vt, vl, and vm, and Debye temperature θD were also reported and analyzed. By incorporating the basic optical properties, we discussed the dielectric function, refractive index, optical reflectivity, absorption coefficient, and optical conductivity in terms of incident photon energy up to 13.5 eV. The present results were found to be in good agreement with the available experimental and other theoretical results.

The CeFe11Ti permanent magnet: a closer look at the microstructure of the compound

High-performance permanent magnets (PM) are compounds with outstanding intrinsic magnetic properties. Most PMs are obtained from a favorable combination of rare earth metals (RE = Nd, Pr, Ce) with transition metals (TM = Fe, Co). Amongst them, CeFe11Ti claims considerable attention due to its large Curie temperature, saturation magnetization, and significant magnetocrystalline anisotropic energy. CeFe11Ti has several potential applications, in particular, in the development of electric motors for future automatic electrification. In this work, we shed some light on the mictrostructure of this compound by performing periodic hybrid-exchange density functional theory (DFT) calculations. We use a combined approach of atom-centered local orbitals, plane waves and full-potential linear muffin-tin orbital (LMTO) for our computations. The electronic configuration of the atoms involved in different steps of formation of the crystal structure of CeFe11Ti gives an explanation on the effect of Ce and Ti on its magnetic properties. While Ti stabilizes the structure, atomic orbitals of Ce hybridizes with Fe atomic orbitals to a significant extent and alters the electronic bands. Our calculations confirm a valence of 3+ for Ce, which has been deemed crucial to obtain a large magnetocrystalline anisotropy. In addition, we analyze several spin configurations, with the ferromagnetic configuration being most stable. We compare and contrast our data to those available and provide an insight for further development of optimized high-performance PMs. Moreover, we compute the Magnetocrystalline Anisotropy of this compound by means of two approaches: the Force Theorem and a full-potential LMTO method.

Theoretical investigation of the structural and electronic properties of BN/GaN superlattices growth along various crystallographic axes

This paper reports first-principles investigations of structural and electronic properties of standard BN/GaN superlattices oriented following the (001), (110) and (111) axes using the full potential linear muffin-tin orbitals method (FPLMTO) in its plane wave approximation (PLW) which enables an accurate treatment of the interstitial regions. The choice of this method ensures the present work to be free from adjustable parameters and enabled us to perform a microscopic study. The results for BN/GaN superlattices with the three directions are investigated and compared. The electronic structure of bulks and also of (001), (110) and (111) growth axis SLs are calculated and it is shown that the (111) growth axis impacts the electronic structure, which indicates a great influence of the p-orbital.

FP-LMTO study of structural, electronic and optical properties of wurtzite (CdS)n/(CdSe)n superlattices

In this paper, we have conducted a first-principles study of the structural, electronic and optical properties of (CdS)n/(CdSe)n superlattices (where n is numbers of monolayers) in the wurtzite phase (B4), using the Full-Potential Linear Muffin-Tin Orbital (FP-LMTO) method within the Local Density Approximation (LDA) technique, in order to describe the exchange correlation energy. The calculated electronic properties indicate that all (CdS)n/(CdSe)n superlattices configurations, possess a semiconductor behavior with same energy gaps. We have seen more carefully and accurately that the different superlattices configurations have no effect on the electronic properties; in particular, we did not observe any dependence between the band gap behavior and the used layers.

An ab initio study of filled skutterudites EuOs4Sb12

The study of structural, elastic, thermodynamic and electronic properties of filled skutterudites EuOs4Sb12 is presented using the full-potential linear muffin-tin orbital method based on the density functional theory. As exchange–correlation potential, we used the local density and local spin density approximation. The equilibrium lattice parameters, bulk modulus, elastic constants and band structure energy of filled skutterudites EuOs4Sb12 are calculated and systematically compared to the available theoretical and experimental data. The total energy variation as a function of strain is used to determine the independent elastic constant and its pressure dependence. The effect of pressure P and temperature T on the lattice parameter, bulk modulus, Debye temperature and the heat capacity of EuOs4Sb12 is investigated for the first time. The electronic band structure shows that EuOs4Sb12 presents a metallic character.

First principle calculations of hydrostatic pressure effect on the Kondo behavior and magnetic properties of CePdBi

In this research, the effect of hydrostatic pressure on the magnetic properties and Kondo behavior of CePdBi compound is studied. To this aim, the pressure dependence of Ce-magnetic moment and hybridization between Ce-4f localized electrons and conduction electrons are investigated. The calculations are performed by using full-potential linear muffin-tin orbital (FP-LMTO) method within density functional theory framework. The exchange-correlation potential is treated within generalized gradient approximation (GGA) and GGA plus U (GGA+U) where U is Hubbard correlation term. The results show that by applying pressure, the hybridization between Ce-4f localized electrons and conduction electrons and consequently the Kondo interaction change; but different behaviors are observed at the positive and negative pressures.

DFT calculations of structural, optoelectronic and thermodynamic properties of BxAl1-xP alloys

The structural, optoelectronic and thermodynamic properties of the ternary alloys BxAl1-xP are investigated using the Full-potential linear muffin-tin orbital (FP-LMTO) method within density functional theory (DFT) in the zinc-blende structure. The exchange and correlation potentials are treated by the local density approximation (LDA) and generalized gradient approximations (GGA). The ground state properties of BxAl1-xP are determined and compared with the available data. The electronic structure have been investigated and discussed in details. The optical constants, including the dielectric function ε(w) and the refractive index n(w) are calculated and we found that our compounds are potential usefulness in optoelectronic applications. Furthermore, we have analyzed the thermodynamic properties by the quasi-harmonic Debye model.

Theoretical study of structural, electronic and optical properties of ScxTl1-xP ternary alloys and (ScP)n/(TlP)n superlattices by FP-LMTO method

The Full Potential Linear Muffin-Tin Orbital (FP-LMTO) method has been used to investigate structural and electronic properties of ScP and TlP binary compounds, their ScxTl1-xP ternary alloys and (ScP)n/(TlP)n superlattices for specific cases of x = 0.25, 0.5, 0.75 and n = 1, 2, 3 in the framework of the density functional theory (DFT) within the local density approximation (LDA). The ground-state properties are determined in the cubic Zinc-blende phase (ZnS).The electronic band structures of ScxTl1-xP ternary alloy were calculated in the Zinc-blende phase and the material has a semi-conductor behavior with a direct band gap for x = 0.25 and an indirect band gap for x = 0.5 and 0.75.In studying the possibility to obtain new materials (ScP)n/(TlP)n, the results show that these materials are semiconductors with an indirect band gap for n = 1 and a direct band gap for n = 2 and 3.The optical properties were calculated for only three materials; Sc0.25Tl0.75P, (ScP)2/(TlP)2 and (ScP)3/(TlP)3 which have a direct band gap.

Band gap behavior of thallium phosphide and gallium phosphide binary compounds and Gax Tl1-x P ternary alloys

Full-potential linear muffin-tin orbitals method has been implanted within density functional theory and within local density approximation. The structural and electronic properties of GaP and TlP binary compounds and their ternary alloys Gax Tl1-x P (x = 0,25, 05 or 0.75) in the zinc-blende structure were investigated and calculations obtained results gave reasonable agreements with other published data.

Effect of spin-orbit interactions on the structural stability, thermodynamic properties, and transport properties of lead under pressure

The paper investigates the role of spin-orbit interaction in the prediction of structural stability, lattice dynamics, elasticity, thermodynamic and transport properties (electrical resistivity and thermal conductivity) of lead under pressure with the FP-LMTO (full-potential linear-muffin-tin orbital) method for the first-principles band structure calculations. Our calculations were carried out for three polymorphous lead modifications (fcc, hcp, and bcc) in generalized gradient approximation with the exchange-correlation functional PBEsol. They suggest that compared to the scalar-relativistic calculation, the account for the SO effects insignificantly influences the compressibility of Pb. At the same time, in the calculation of phonon spectra and transport properties, the role of SO interaction is important, at least, for $P\ensuremath{\lesssim}150$ GPa. At higher pressures, the contribution from SO interaction reduces but not vanishes. As for the relative structural stability, our studies show that SO effects influence weakly the pressure of the $\mathrm{fcc}\ensuremath{\rightarrow}\mathrm{hcp}$ transition and much higher the pressure of the $\mathrm{hcp}\ensuremath{\rightarrow}\mathrm{bcc}$ transition.