Full-potential Linear Muffin-tin Orbital Research Articles

Structural and electronic properties of ScxAl1−xN: First principles study

The structural and electronic properties of ScxAl1−xN ternary semiconductor alloys are investigated in the rocksalt, zinc blend and wurtzite structures using the full potential linear muffin tin orbitals (FP-LMTO) method. The local density approximation (LDA) was used for the exchange and correlation energy density functional. In particular, the lattice constant, bulk modulus and band gap energies of ScN and AlN compounds and their ternary alloys ScxAl1−xN are calculated in rocksalt, zinc blend and wurtzite structures and discussed. A linear relationship has obtained for equilibrium lattice constants versus Sc concentration for rocksalt and zinc blend structures. The band gap is decreased with the increasing of Sc concentration in the rocksalt phase. For ZB-ScxAl1−xN, the band gap is the largest one at x=0.25 and changes from indirect to direct when x is more than 0.25.

Structural and Electronic Properties Calculations of AlAs<SUB>1-x</SUB>P<SUB>x</SUB> Alloy

Based on the self-consistent ab initio the full-potential linear muffin-tin orbital (FP-LMTO) method, the structural, electronic, optical, and thermodynamic properties of AlAs<SUB>1-x</SUB>P<SUB>x</SUB> ternary semiconductor alloys have been investigated. The exchange–correlation potential was calculated using both the local density approximation (LDA) and generalized gradient approximation (GGA). The ground-state properties are determined for the cubic bulk materials AlAs, AlP, and their mixed crystals at various concentrations (x = 0.25, 0.5, and 0.75). Deviation of the lattice parameter from Vegard’s law and the bulk modulus from linear concentration dependence has been examined. The microscopic origins of the band-gap bowing parameter have been discussed. Moreover, the refractive index for AlAs<SUB>1-x</SUB>P<SUB>x</SUB> is studied using Reedy and Nazeer model. Besides, the thermodynamic stability of the alloys of interest is investigated by means of the miscibility critical temperature.

Computational Investigation of Electronic and Optical Properties of Si, Ge and Si1-xGex Alloys Using the FP-LMTO Method Augmented by a Plane-Wave Basis

An investigation into the structural, electronic and optical properties of Si, Ge, and Si1-xGex for different compositions was conducted using first-principles calculations based on density functional theory (DFT). The total energies were calculated within the full -potential linear muffin-tin orbital (FP-LMTO) method augmented by a plane-wave basis (PLW), implemented in Lmtar code. The effects of the approximations to the exchange-correlation energy were treated by the local density approximation (LDA). From our simulation results, it is found that the theoretical ground-state parameters, the band structure, the density of states (DOS), the chemical bonding and the optical properties agree well with the experi- ment and other theoretical calculations. The accuracies found from the present calculations allow us to describe the proper- ties of the electronic as well as the optoelectronic devices based on the Si1-xGex alloy.

Crystallographic input data for (001)-, (110)- and (111)-oriented superlattices

General aspects concerned with (001)-, (110)- and (111)-oriented superlattices (SLs) have been investigated. In particular, the symmetry of these systems have been derived and given in detail. As a test, the obtained data have been utilized to calculate electronic structures and gaps of a standard GaAs/AlAs system using an accurate version of the first principle full potential linear muffin-tin orbital (FPLMTO) method based on a local-density functional approximation (LDA).

Structural and optoelectronic properties of NiTiX and CoVX (X = Sb and Sn) half-Heusler compounds: An ab initio study

We have performed ab-initio self-consistent calculations using the full-potential linear muffin-tin orbital (FP-LMTO) method to investigate the structural and the electronic properties of some half-Heusler alloys. The local density and generalized gradient approximations were used for NiTiSn and CoVSn alloys. Due to the metallic characters of both NiTiSb and CoVSb compounds, the local spin density approximation was used. Lattice constants, bulk moduli, and the pressure derivatives of the bulk moduli are calculated, band structure and density of states are drawn and effective masses are investigated. To our knowledge this is the first quantitative theoretical prediction of the effective masses for the investigated compounds and still awaits experimental confirmations. The obtained results are agreed well with the other published values.

Theoretical Study on the Origins of the Gap Bowing in Mg&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt;Zn&amp;lt;sub&amp;gt;1–x&amp;lt;/sub&amp;gt;O Alloys

The full potential linear muffin-tin orbital (FP-LMTO) method was applied to study the structural and electronic properties of the compounds MgO, ZnO and their alloy MgxZn1–xO in the zincblende and NaCl structures. Results are obtained using the local density approximation (LDA), the ground-state properties like lattice constant and bulk modulus obtained agree very well with experimental and other theoretical calculations. The effect of composition on lattice constant from Vegard’s law and the bulk modulus was investigated. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. It is concluded that the energy band gap bowing is primarily due to chemical charge-transfer effect. Contribution of volume deformation and structural relaxation to the gap bowing parameter is found to be very small.

&amp;lt;i&amp;gt;Ab Initio&amp;lt;/i&amp;gt; Calculations Study of Structural and Electronic Properties of Ternary Alloy Al&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt;In&amp;lt;sub&amp;gt;1–x&amp;lt;/sub&amp;gt;As

First principles calculations of the structural and electronic properties of AlAs, InAs and their alloy AlxIn1–xAs have been performed using the full-potential linear muffin-tin orbital (FP-LMTO) [1] method within density functional theory (DFT) [2,3]. We used the local density approximation (LDA) [4] within the generalized gradient correction (GGA) [5] to calculate the electronic structure at equilibrium volume. The effect of composition on lattice constants, bulk modulus and band gap were investigated. Deviations of the lattice constants from Vegard’s law and the bulk modulus were observed for this alloy. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers [6-9].

Physical Properties of the Zn&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt;Cd&amp;lt;sub&amp;gt;1-x &amp;lt;/sub&amp;gt;Se Alloys: Ab-Initio Method

The present work performs self-consistent ab initio full-potential linear muffin-tin orbital (FP-LMTO) method to study the structural and electronic properties of the ternary ZnxCd1-xSe alloy, based on density functional theory (DFT). In this approach, both the local density approximation (LDA) and the generalized gradient approximation (GGA) were used for the exchange-correlation potential calculation. The ground-state properties are determined for the bulk materials CdSe, ZnSe and their alloy in cubic phase. In particular, the lattice constant, bulk modulus, electronic band structures and effective mass. We mainly showed deviation of the lattice parameter and bulk modulus from Vegard’s law of our alloys. We also presented the microscopic origins of the gap bowing using the approach of Zunger et al. The results are compared with other theoretical calculations and experimental data and are in reasonable agreement.

FP-LMTO Calculations of Structural and Electronic Properties of Alkaline-Earth Chalcogenides Alloys AY:A = Ca, Sr, Ba; Y = S

The structural and the electronic properties of the ternary SrxCa1-xS, BaxCa1-xS and BaxSr1-xS alloys have been calculated using the full-potential linear muffin-tin-orbital (FP-LMTO) method based on density functional theory, within both local density approximation (LDA) and generalized gradient approximation (GGA). The calculated equilibrium lattice constants and bulk modulus are compared with previous results. The concentration dependence of the electronic band structure and the direct and indirect band gaps are investigated. Using the approach of Zunger and co-workers, the microscopic origins of the band gap bowing are investigated also. A reason is found from the comparison of our results with other theoretical calculations.

Theoretical investigation of the elastic, thermodynamic, electronic and magnetic properties of PrNi 2Si 2 and PrNi 2Ge 2

The structural, elastic, thermodynamic, electronic and magnetic properties of ferromagnetic tetragonal PrNi 2Si 2 and PrNi 2Ge 2 compounds have been calculated using the full-potential linear muffin-tin orbital (FP-LMTO) method. The exchange–correlation potential is treated within the local spin density approximation of Perdew and Wang (LSDA–PW). Moreover, we have added the Coulomb interaction U to improve the electronic band structure calculations and the magnetic properties. The calculated structural parameters are in good agreement with the experimental data. The elastic constants C ij are predicted using the total energy variation versus strain technique. The polycrystalline elastic moduli, namely; shear modulus, Young’s modulus, Poisson’s ratio, sound velocities and Debye temperature are derived from the obtained single-crystal elastic constants. Ductility behavior of these compounds is interpreted via the calculated elastic constants C ij . Electronic and bonding properties are discussed from the calculations of band structure and density of states. The thermodynamic properties are predicted through the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variation of the bulk modulus, lattice constant, heat capacities and Debye temperature with pressure and temperature are successfully obtained.

The Coulomb Interaction and Volume Compression Effect on Spin and Orbital Magnetic Moment of NiO

This calculation focuses on the effect of the Coulomb interaction U and the volume compression (VC) on both spin (m(s)) and orbital (m(o)) magnetic moment of NiO by using the local spin density approximation plus the Coulomb interaction (LSDA + U) method within full potential linear muffin-tin orbital (FP-LMTO). Our calculated results indicated that both spin and orbital magnetic moment strongly correlated to U and VC. The relevant results exhibited the increasing spin and orbital magnetic moments with increasing Coulomb interaction and decreasing volume compression. The interesting behavior appears when volume compression is greater than 70% at which m(s) collapses whereas m(o) linearly decreases. Further increase of volume compression to be at 80% leads to the disappearance of both magnetic moments. The present results exhibit the good correspondence to the experimental data at the normal pressure and U value of 6 eV.

Coulomb and Exchange Interaction Effect on Magnetic Properties of MnO

This calculation focus on the effect of Coulomb interaction U and exchange interaction J on spin magnetic moment Ms of MnO by using the local spin density approximation plus the Coulomb interaction (LSDA+U) method within full potential linear muffin-tin orbital (FP-LMTO). Our calculated results indicated that the spin magnetic moments correlated to U and J. The relevant results exhibited the increasing spin magnetic moments with increasing Coulomb interaction and exchange interaction. Furthermore, equation of spin magnetic moments, which good correspondence to the experimental data, were obtained and the relation of U and J parameter was defined.

First-principles study of structural, electronic and magnetic properties in Cd1−xFexS diluted magnetic semiconductors

In this paper, we report theoretical investigations of structural, electronic and magnetic properties of ordered dilute ferromagnetic semiconductors Cd1−xFexS with x=0.25, 0.5 and 0.75 in zinc blende (B3) phase using all-electron full-potential linear muffin tin orbital (FP-LMTO) calculations within the density functional theory and the generalized gradient approximation. The analysis of band structures, density of states, total energy, exchange interactions and magnetic moments reveals that both the alloys may exhibit a half-metallic ferromagnetism character. The value of calculated magnetic moment per Fe impurity atom is found to be 4μB. Moreover, we found that p–d hybridization reduces the local magnetic moment of Fe from its free space charge value of 4μB and produces small local magnetic moments on Cd and S sites.

Structural properties and new phase transitions of ScN using FP-LMTO method

By full potential linear muffin-tin orbitals (FP-LMTO) method, we have studied the phase transitions of ScN under high pressures. The local density (LDA) approximation was used for the exchange and correlation energy density functional. The most important result is the prediction of the possibility of two phase transitions from the cubic rocksalt (NaCl) structure to the orthorhombic CaSi (Cmmc) structure above 252.5 GPa and to the tetragonal AuCu (P4/mmm) structure at 303.017 GPa, the first one (NaCl–CaSi) occurring at a lower pressure than the well known NaCl to CsCl transition (found here to be 324 GPa).

Thermodynamic Properties of AlNi Intermetallics under High Pressure

The thermodynamic properties of AlNi are investigated by the full-potential linearized muffin-tin orbital (FP-LMTO) scheme within the generalized gradient approximation correction (GGA) in the frame of density functional theory. The calculated lattice parameter and bulk modulus are in excellent agreement with the experimental and other calculated results. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the dependences of relative volumeV/V0on pressureP, cell volumeVon temperatureT, linear thermal expansion α and specific heatCVon temperature and pressure are successfully obtained.

FIRST PRINCIPLES STUDY OF THE STRUCTURAL, ELASTIC AND ELECTRONIC PROPERTIES OF Ti2InC and Ti2InN

The structural, elastic and electronic properties of Ti 2 InC and Ti 2 InN compounds have been calculated using the full-potential linear muffin-tin orbital (FP-LMTO) method. The exchange and correlation potential is treated by the local density approximation (LDA). The calculated ground state properties, including, lattice constants, internal parameters, bulk modulus and the pressure derivative of the bulk modulus are in reasonable agreement with the available data. The effect of pressure, up to 40 GPa, on the lattice constants and the internal parameters is also investigated. Using the total energy-strain technique, we have determined the elastic constants Cij, which have not been measured yet. The band structure and the density of states (DOS) show that both materials have a metallic character and Ti 2 InN is more conducting than Ti 2 InC . The analysis of the site and momentum projected densities shows that the bonding is achieved through a hybridization of Ti -atom d states with C ( N )-atom p states. Otherwise, it has been shown that Ti – C and Ti – N bonds are stronger than Ti – In bonds.

Structural and Electronic Properties Calculations of Al &amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt;In&amp;lt;sub&amp;gt;1-x &amp;lt;/sub&amp;gt;P Alloy

The equilibrium structure and the electronic properties of III-V zinc-blende AlP, InP semiconductors and their alloy have been studied in detail from first-principles calculations. A full-potential linear muffin-tin-orbital (FP-LMTO) method has been used in conjunction with both the local-density approximation (LDA) and the generalized-gradient approximation (GGA) to investigate the effect of increasing the concentration of aluminum on the structural properties such as the lattice constants and the bulk moduli. Besides, we report the concentration dependence of the electronic band structure, the direct-indirect band gap crossovers and bowing. Using the approach of Zunger and co-workers the microscopic origins of the gap bowing were also explained. A reasonable agreement is found in comparing our results with other theoretical calculations.

FP-LMTO Investigation of the Structural and Electronic Properties of Cu&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt;Ag&amp;lt;sub&amp;gt;1–x&amp;lt;/sub&amp;gt;I Alloys

The structural and electronic properties of the ternary CuxAg1–xI, alloy have been calculated, using the full-potential linear muffin-tin-orbital (FP-LMTO) method based on density functional theory, within both the local density approximation and the generalized gradient approximation (GGA). The equilibrium lattice constants and the bulk modulus are compared with previous theoretical calculations. The concentration dependence of the electronic band structure and the direct-indirect band gaps is also investigated. Using the approach of Zunger and co-workers the microscopic origins of the gap bowing were also explained.

Structural and electronic properties of bulk GaP and AlP and their [formula omitted] superlattices

The structural and the electronic properties of binary GaP and AlP compounds and their ( GaP ) n / ( AlP ) n superlattices are investigated using the recent version of the first-principles full potential linear muffin-tin orbitals method (FP-LMTO) (Lmtart 7.0). The structural parameters and the pressures at which these compounds undergo structural phase transition from zinc-blende (B3) to the rocksalt (B1) are determined. From the results of the electronic properties we find that the parent materials (GaP, AlP) have indirect bandgaps. The resemblances between GaP and AlP and their small lattice mismatch led us to perform investigations on zinc-blende/zinc-blende ( GaP ) n / ( AlP ) n for n = 1 , 2 and 3 monolayer. Our calculations performed for band structure and density of state show an indirect band gap superlattices for n = 1 and 2 and a direct band gap for n = 3 . Details of the electronic structure of superlattices are discussed. An excellent agreement was found between our results and those of other theoretical predictions and experimental measurements.

Equation of state for ε-iron at high pressures and temperatures

The equation of state for hexagonal close packed (hcp or ∈) phase of Fe at high pressure is created by employing molecular dynamics (MD) simulations in conjunction with the embedded atom method based on the full potential linear muffin tin orbital (FPLMTO) method. Comparison between the existing experimental data and our calculations suggests that the obtained equation of state can be reliably used for calculating iron volumetric properties under conditions appropriate for the Earth's core. We demonstrate that some experimental data on iron might be subjected to a systematic error. I suggest a model which describes the temperature dependence of the volume better than the Mie-Gruneisen equation.