Full-potential Linear Muffin-tin Orbital Method Research Articles

First-principles calculations of the band ordering conversion in the [formula omitted] compounds

Topological insulators (Tls) are new kinds of quantum's materials states discovered recently, with insulating bulk band gaps and topologically protected metallic surface states; they are immensely investigated due to their promising characteristics for spintronic and quantum computing applications. In this work, we study the potential of Tl property in inverses Heusler compounds (LaxSc2−xRuPb) with x = 0, 1 and 2, by first-principles calculations within the full-potential linear muffin-tin orbital (FP-LMTO) computational approach method as implemented in the computer code (LMTART), which is based on the density functional theory (DFT). We used the local-density approximation (LDA) for the term of the exchange and correlation potential (XC). We investigate the topological ordering of quaternary inverse Heusler XX’YZ according to the possible X and X′ sites combination, and we focus that the trivial semiconductors compounds in x = 0, 2 with the positive energy difference (ΔE=EΓ6−EΓ8) exhibit a non trivial candidates in x = 1 with EΓ6−EΓ8<0.

Electronic structure properties of new equiatomic CoCuMnZ (Z=In, Sn, Sb) quaternary Heusler alloys: An ab-initio study

The electronic structure, elastic, magnetic and exchange coupling properties of new equiatomic quaternary Heusler alloys CoCuMnZ (for Z = In, Sn, Sb) have been studied using the full-potential linear muffin-tin orbital method. Total energy calculations show that formation of these alloys are energetically favorable and that they are stable in the ferromagnetic phase. Total density of states establish that CoCuMnIn and CoCuMnSn possess metallic behavior at equilibrium lattice constant and show half metallicity on lattice compression. CoCuMnSb is a true half metallic at the equilibrium lattice constants with an indirect band gap of ∼0.5 eV. The calculated values of elastic constants show that CoCuMnIn/Sn also have mechanical stability. In CoCuMnZ, Co-Mn, Mn-Mn and Mn-Co couple ferromagnetically resulting in high Curie temperature in these alloys.

Structural, Elastic, and Electronic Properties of CeN and LuN Using: Ab Initio Study

We report on the electronic, structural, and elastic property calculations conducted for the rare-earth (RE) nitride compounds in the rocksalt structure (CeN and LuN compounds) using the full-potential linear muffin-tin orbital method (FP-LMTO) based on the spin density functional theory (DFT) calculations using the LSDA + U approach (local spin density approximation with Hubbard-U corrections). The LSDA + U approximation is applied to the 4f as well as 5d states. Various space groups were considered including the NaCl (Fm-3m (225)), the cesium chloride [CsCl(Pm-3m (221))], and the zinc blende [ZnS(F-43m 216))]. Our obtained results indicate that the NaCl-type structure is stable than all the other phases, while the predicted elastic constants were found to satisfy the mechanical stability. The related mechanical properties such as the anisotropy factor (A), Poisson’s ratio (υ), Young’s modulus (E), and the shear modulus (G) for the same NaCl structure were also calculated. Finally, the band structure calculations of the CeN and LuN have revealed half-metallic and semiconductor behaviour, respectively. The obtained results are presented and in-depth discussed.

Effects of temperature and pressure on thermodynamic properties of Cd0.25Zn0.75Se alloy

Thermodynamic properties of Cd0.25Zn0.75Se alloy are studied using quasi harmonic model for pressure range of 0 GPa−10 GPa and temperature range 0 K−1000 K. The structural optimization is obtained by self-consistent field calculations and full-potential linearized muffin-tin orbital method with GGA+U as an exchange correlation functional where U = 2.3427 eV is Hubbard potential. The effects of temperature and pressure on bulk modulus, Helmholtz free energy, internal energy, entropy, Debye temperature, Grüneisen parameter, thermal expansion coefficient, and heat capacities of the material are observed and discussed. The bulk modulus, Helmholtz free energy, and Debye temperature are found to be decreased on increasing temperature while there is an increasing behavior with rise of the pressure. Whereas the internal energy has increasing trend with the rise in temperature and it almost remains insensitive to pressure. The entropy of the system increases (decreases) with rise of pressure (temperature).

Structural and electronic properties of CuxAg1-xCl: First-principles study

The structural and electronic properties of the ternary $\rm{Cu}_{x}\rm{Ag}_{1-x}\rm{Cl}$ alloy are investigated using a recent version of the full potential linear muffin-tin orbitals method (FPLMTO) based on the density functional theory, within both the local density approximation (LDA) and the generalized gradient approximation (GGA). The lattice constants, bulk modulus and band gap were calculated as a function of copper molar fraction x in rock salt (B1) and zincblende (B3) structures. These parameters were found to depend non-linearly on alloy concentration Cu, except for the lattice parameter which follows Vegard’s law. Our results predict the rock salt phase as the ground state for this ternary system.

Effects of temperature and pressure on thermodynamic properties of Cd0.50 Zn0.50 Se alloy

Thermodynamic properties of Se alloy are studied using quasi harmonic model for pressure range 0–10 GPa and temperature range 0–1000 K. The structural optimization is obtained by self consistent field calculations and full-potential linear muffin-tin orbital method with GGA+U as an exchange correlation functional where eV is the hubbard potential. The effects of temperature and pressure on the bulk modulus, Helmholtz free energy, internal energy, entropy, Debye temperature, Grüneisen parameter, thermal expansion coefficient and heat capacities of the material are observed and discussed. The bulk modulus, Helmholtz free energy and Debye temperature are found to decrease with increasing temperature while there is an increasing behavior when the pressure rises. Whereas internal energy has increasing trend with rises in temperature and it almost remains insensitive to pressure. The entropy of the system increases (decreases) with a rise of pressure (temperature).

First-Principle Study of the Electronic and Magnetic Properties of Nd1−x La x FeSi Alloys (x = 0, 0.25, 0.50, 0.75, and 1)

The structural, electronic, and magnetic properties of Nd1−x La x FeSi (x = 0, 0.25, 0.50, 0.75, and 1) alloys are investigated based on the first-principle density functional theory by using the full-potential linear muffin-tin orbital (FP-LMTO) method. The exchange-correlation potential is treated with local density approximation (LDA). In addition, to treat localization of 4f-electrons properly, the LDA + U approach (where U is the Hubbard correlation term) is also employed. The calculated structural, electronic, and magnetic properties of these alloys within LDA and LDA + U approaches are compared. The calculated lattice constants of these alloys as a function of x within the LDA + U approach are in the best agreement with linear Vegard’s rule. Most importantly, we focus on the magnetic properties of these alloys and find that the magnetic interaction between Nd atoms is the Rudermen-Kittel-Kasuya-Yosida (RKKY) interaction type. Iron does not carry magnetic moment in these alloys and has just an induced small magnetic moment from Nd atoms.

FPLMTO study of new phase changes in CuX (X = Cl, Br, I) compounds under hydrostatic pressure

We study the ground-state properties of copper halides CuX (X = Cl, Br, I) and the behavior under pressure using a recent version of the full potential linear muffin-tin orbitals method (FPLMTO). It predicts the possibility of an additional local minimum in the tetragonal PbO phase for CuBr and CuI at 0.7 GPa and 01.53 GPa with a direct energy gap at Γ of about 0.678 eV and 1.265 eV respectively. The use of GGA in this work is more appropriate than LDA and correctly predicts the cubic B3 phase as ground state structure for the three binaries. Importantly, calculated transition pressure Pt revealed also the presence of PbO phase at 5.333 GPa for CuCl which is consistent with experimental reports. Other important results are that concerned with the possibility of phase transition from B3 to the hexagonal B8 phase at lower pressures (3.43, 4.11 and 6.23) GPa and from B3 to B2 at (22.96, 22.66 and 24.83) GPa respectively for CuBr, CuI and CuCl.

Ab Initio Study of Electronic Structure, Elastic and Transport Properties of Fluoroperovskite LiBeF3

The aim of this work is to investigate the electronic, mechanical, and transport properties of the fluoroperovskite compound LiBeF3 by first-principles calculations using the full-potential linear muffin-tin orbital method based on density functional theory within the local density approximation. The independent elastic constants and related mechanical properties including the bulk modulus (B), shear modulus (G), Young’s modulus (E), and Poisson’s ratio (ν) have been studied, yielding the elastic moduli, shear wave velocities, and Debye temperature. According to the electronic properties, this compound is an indirect-bandgap material, in good agreement with available theoretical data. The electron effective mass, hole effective mass, and energy bandgaps with their volume and pressure dependence are investigated for the first time.

Comparative study on performance and physical properties of CsI, NaI, RbI, and KBr materials

In the present work we report the results of our investigation using the full potential linear muffin tin orbital method (FP-LMTO) to calculate the structural and electronic properties of NaI, KBr, RbI, and CsI materials, in particular, the lattice constant and bulk modulus. The electronic band structures are also studied and discussed. Our aim is to find the relationship between the physical properties of these materials and their efficiency for detection. For this, Geant4 simulation has been performed for studying the absolute and photopeak detection efficiencies for the different materials as scintillation detectors at several photon energies. The range of gamma ray energy was between 662 and 1332.5 keV. The measurement results are compared with the available theoretical and experimental data.

Elastic and electronic properties calculations of the filled skutterudite CeOs4P12

The full-potential linear muffin-tin orbital method (FP-LMTO) within the local density approximation (LDA) using the Perdew-Wang parameterization is used to calculate the structural, electronic and elastic properties of the filled skutterudite CeOs4P12. The results of the electronic properties show that this compound is an indirect band gap material (T -N). A special interest has been made to the determination of the elastic constants since there have been no available experimental and theoretical data. The energy band gaps and their volume and pressure dependence are also investigated.

Electronic band structure ofMg−IV−N2compounds in the quasiparticle-self-consistentGWapproximation

We present calculations of the lattice constants, structural parameters, bulk moduli, energies of formation, and band structures of $\mathrm{Mg}\ensuremath{-}\mathrm{IV}\ensuremath{-}{\mathrm{N}}_{2}$ compounds with IV=Si, Ge, Sn by using the full-potential linearized muffin-tin orbital method and the quasiparticle-self-consistent $GW$ approach for the wurtzite-based $Pna{2}_{1}$ crystal structure. The lattice parameters calculated with the generalized gradient approximation (GGA) are found to be in good agreement (within 1%) with experiment for the cases of ${\mathrm{MgSiN}}_{2}$ and ${\mathrm{MgGeN}}_{2}$, where data are available. Similar to the Zn-IV-${\mathrm{N}}_{2}$ compounds, ${\mathrm{MgSiN}}_{2}$ is found to have an indirect gap slightly lower than the lowest direct gap, while the other materials have direct gaps. The direct gaps, calculated at the GGA lattice constant, range from 3.43 eV for ${\mathrm{MgSnN}}_{2}$ to 5.14 eV for ${\mathrm{MgGeN}}_{2}$ and 6.28 eV for ${\mathrm{MgSiN}}_{2}$ in the $0.8\mathrm{\ensuremath{\Sigma}}$ approximation, i.e., reducing the $\mathrm{QS}GW\phantom{\rule{4pt}{0ex}}\mathrm{\ensuremath{\Sigma}}$ by a factor 0.8 and including an estimated zero-point-motion correction. The symmetry character of the valence-band maximum states and their splittings and effective masses are determined. The conduction-band minima are found to have slightly higher Mg $s$- than Si $s$-like character in ${\mathrm{MgSiN}}_{2}$ but in ${\mathrm{MgGeN}}_{2}$ and ${\mathrm{MgSnN}}_{2}$, the group-IV-$s$ character becomes increasingly dominant.

Comment on “Structural, electronic, elastic, optical and thermodynamic properties of copper halides CuCl, CuBr and their ternary alloys CuCl1−xBrx (0.0 ≤ x ≤ 1.0) using full-potential linear muffin-tin orbital (FP-LMTO) method”[Optik 127 (2016) 4559–4573

Kamel et al. (2016) [1] have recently published a paper in Optik 127 (2016) 4559–4573. They have studied several interesting properties, such as: structural, elastic, electronic, optical and thermodynamic properties of copper halides (CuCl, CuBr and their ternary alloys CuCl1−xBrx (0.0≤x≤1.0)) using full-potential linear muffin-tin orbital (FP-LMTO) method. After carefully reading the paper of Kamel et al. (2016), it is observed that the algebraic values of the longitudinal (vl), transverse (vt) and average (vm) wave velocities, and also that of the Debye temperature θD, of CuX (X=Cl, Br) binary compounds obtained in the paper Kamel et al. (2016) [1] are not correctly calculated. Although this mistake has no influence on the conclusion of the paper Kamel et al. (2016) [1], I think, that is better to correct the numerical values of the previous quantities, which can be reused in the future by other researchers, perhaps for comparison or for other object.In the present work, I recalculate the correct numerical values of the longitudinal (vl), transverse (vt) and average (vm) wave velocities, and the Debye temperature θD, of CuX (X=Cl, Br) compounds, using the lattice parameters and the elastic moduli obtained in the original work of Kamel et al. (2016) [1].

Structural, elastic, thermodynamic and electronic properties of LuX (X = N, Bi and Sb) compounds: first principles calculations

ABSTRACTThe structural, electronic, elastic and thermodynamic properties of LuX (X = N, Bi and Sb) based on rare earth into phases, Rocksalt (B1) and CsCl (B2) have been investigated using full-potential linearized muffin-tin orbital method (FP-LMTO) within density functional theory. Local density approximation (LDA) for exchange-correlation potential and local spin density approximation (LSDA) are employed. The structural parameters as lattice parameters a0, bulk modulus B, its pressure derivate B’ and cut-off energy (Ec) within LDA and LSDA are presented. The elastic constants were derived from the stress–strain relation at 0 K. The thermodynamic properties for LuX using the quasi-harmonic Debye model are studied. The temperature and pressure variation of volume, bulk modulus, thermal expansion coefficient, heat capacities, Debye temperature and Gibbs free energy at different pressures (0–50 GPa) and temperatures (0–1600 K) are predicted. The calculated results are in accordance with other data.

Structural, electronic, elastic, optical and thermodynamic properties of copper halides CuCl, CuBr and their ternary alloys CuCl1−xBrx (0.0 ≤ x ≤ 1.0) using full-potential linear muffin-tin orbital (FP-LMTO) method

The structural, electronic, elastic, and thermodynamic properties of alloy CuCl1−xBrx in B3 (zinc blend) phase are investigated to investigate the effect of substitution of Br in CuCl in the range 0≤x≤1. For this purpose, first-principal calculations are used via the full-potential linear muffin-tin orbital (FP-LMTO). The exchange and correlation energy is described in the generalized gradient approximation (GGA). The effect of composition on lattice constant, bulk modulus and band gap is investigated. The concentration dependence of the electronic band structure and the direct-indirect band gap structures are also investigated. Using the approach of Zunger and co-workers, the microscopic origins of band gap bowing parameter have been interpreted. The refractive index, electron (hole) and valence effective masses are also calculated. Furthermore, thermodynamic stability of CuCl1−xBrx ternary alloys is studied by calculating the excess enthalpy of mixing ΔHm as well as the phase diagram.

Ab initio calculations of structural, elastic, electronic and thermodynamic properties of the cerium filled skutterudite CeRu4P12 under the effect of pressure

AbstractThe paper presents an investigation on crystalline, elastic and electronic structure in addition to the thermodynamic properties for a CeRu4P12 filled skutterudite device by using the full-potential linear muffin-tin orbital (FP-LMTO) method within the generalized gradient approximations (GGA) in the frame of density functional theory (DFT). For this purpose, the structural properties, such as the equilibrium lattice parameter, bulk modulus and pressure derivatives of the bulk modulus, were computed. By using the total energy variation as a function of strain we have determined the independent elastic constants and their pressure dependence. Additionally, the effect of pressure P and temperature T on the lattice parameters, bulk modulus, thermal expansion coefficient, Debye temperature and the heat capacity for CeRu4P12 compound were investigated taking into consideration the quasi-harmonic Debye model.

Half-metallic properties and the robustness of Co2MnGe Heusler alloy under pressure: Ab-initio calculation

To investigate the structural, mechanical, electronic and magnetic properties of full Heusler Co2MnGe in L21 structure, we used first-principle calculations. We made use of all-electron full potential linearized muffin-tin orbital method (FP-LMTO) within the density functional theory. The generalized gradient approximation GGA allows describing the exchange correlation energy. The obtained lattice parameters, bulk modulus and its derivate are in good agreement with experimental and theoretical values. We have also calculated the elastic constants and their related parameters. GGA + U approach allows to process electronic properties. For our compound, the band structure and magnetic moments are treated at equilibrium lattice constant. At Fermi level, the material has a semi metallic behavior with 100% spin polarization ratio. Computed magnetic exchange constants are used to evaluate the Curie temperature from mean field-approximation (MFA). Finally the elastic constants, electronic structure and magnetic properties are investigated at high-pressure. We noticed that half-metal to metal transition was around 102 GPa. The increasing pressure does not affect-the total magnetic moment and the overall shape of the band structure which indicates the robustness of electronic structure of this system.

Ab Initio Study of the Structural, Electronic, and Thermal Properties of $$\hbox {BaS}_{{1-{{x}}}}\hbox {Te}_{{x}}$$ BaS 1 - x Te x Alloy

The results of a first-principle study of the structural, electronic, and thermal properties of a $$\hbox {BaS}_{1-{x}}\hbox {Te}_{{x}}$$ alloy, using the full-potential linear muffin-tin-orbital (FP-LMTO) method in the framework of density functional theory, within both the local density approximation and the generalized gradient approximation are presented. The composition effect on lattice constants, bulk moduli, band gaps, and effective masses is analyzed. The quasi-harmonic Debye model, using a set of total energy versus volume calculations obtained with the FP-LMTO method, is applied to study the thermal and vibrational effects. The temperature effect on the lattice parameters, thermal expansions, heat capacities, and Debye temperatures is determined from the non-equilibrium Gibbs functions. The microscopic origins of the bowing parameter were explained using the approach of Zunger and coworkers.

Structural, Electronic, Optical, and Thermodynamic Properties of Copper Halide CuCl_(1-x)I_x (0.0 ≤ x ≤ 1.0) Ternary Alloy: First Principal Calculations

First-principles calculations of the structural and electronic properties of CuCl_(1-x)I_x ternary alloys for variable doping concentrations (x), using the full-potential linear muffintin-orbital (FP-LMTO) method based on density functional theory (DFT) within the generalized gradient approximation (GGA), are presented. The equilibrium lattice constants and the bulk modulus are compared with other results. The concentration dependence of the electronic band structure and the direct-indirect band gap structures are also investigated. Using the approach of Zunger and coworkers, the microscopic origins of the band gap bowing parameter have been interpreted. Furthermore, the thermodynamic stability of CuCl_(1-x)I_x ternary alloys is studied by calculating the excess enthalpy of mixing ΔHm as well as the phase diagram. A reasonable agreement is found from the comparison of the present first-principles calculations with other experimental and theoretical data.

Exchange parameters of strongly correlated materials: Extraction from spin-polarized density functional theory plus dynamical mean-field theory

In this paper we present an accurate numerical scheme for extracting interatomic exchange parameters (${J}_{ij}$) of strongly correlated systems, based on first-principles full-potential electronic structure theory. The electronic structure is modeled with the help of a full-potential linear muffin-tin orbital method. The effects of strong electron correlations are considered within the charge self-consistent density functional theory plus dynamical mean-field theory. The exchange parameters are then extracted using the magnetic force theorem; hence all the calculations are performed within a single computational framework. The method allows us to investigate how the ${J}_{ij}$ parameters are affected by dynamical electron correlations. In addition to describing the formalism and details of the implementation, we also present magnetic properties of a few commonly discussed systems, characterized by different degrees of electron localization. In bcc Fe, treated as a moderately correlated metal, we found a minor renormalization of the ${J}_{ij}$ interactions once the dynamical correlations are introduced. However, generally, if the magnetic coupling has several competing contributions from different orbitals, the redistribution of the spectral weight and changes in the exchange splitting of these states can lead to a dramatic modification of the total interaction parameter. In NiO we found that both static and dynamical mean-field results provide an adequate description of the exchange interactions, which is somewhat surprising given the fact that these two methods result in quite different electronic structures. By employing the Hubbard-I approximation for the treatment of the $4f$ states in hcp Gd we reproduce the experimentally observed multiplet structure. The calculated exchange parameters result in being rather close to the ones obtained by treating the $4f$ electrons as noninteracting core states.