Linear Muffin-tin Orbital Method Research Articles

Electrical and Magnetic Properties of Rough Alloyed Interface of Fe/Co.

We investigated the electronic structure of rough interfaces in random Co/Fe  alloys, where cobalt (Co) was deposited on an iron (Fe) substrate with varying composition ratios. To model the rough surface, we utilized a coupled continuum equation as described by Huda. The electronic properties, specifically the density of states of these random alloys, were calculated using the augmented space recursion method in conjunction with the Linear Muffin-tin Orbital (LMTO) Method. Furthermore, we analyzed the magnetic and electronic properties derived from the calculated density of states.

Ab-initio prédiction of the structural ,electro-magnetic and thermodynamic properties of Co-based Full Heusler alloy

The structural, thermodynamic, electronic, magnetic and elasticproperties of the Full-Heusler Co2MnTi compoundon the cobalt (Co) are determined byusing first-principles calculations based on density functional theory (DFT). We have used the linear Muffin-Tin Orbitals method (FP-LMTO) combined with the generalized gradient approximation (GGA) with spin. The obtained results demonstrate that our material is ferromagnetic and exhibits metallic behavior around the Fermi level .The study of the elastic properties show that Co2MnTi is mechanically stable and is also classified as a ductile material. The GIBBS program is used to comput the thermodynamic properties such as the modulus of compressibility, the heat capacity volume and pressur, the thermal expansion, the Debye temperature and the volume variation at constants. This type of material is considered as promising for spintronic applications.

Electronic structure and resonant inelastic x-ray scattering in Ca3Ru2O7

We have investigated the electronic structure of the transition metal oxide Ca3Ru2O7 within density-functional theory using the generalized gradient approximation while considering strong Coulomb correlations in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band structure method. Ca3Ru2O7 can be classified as a Mott insulator since it was expected to be metallic from band structure calculations. We found that the magnetic ground state of Ca3Ru2O7 possesses an AFM−b magnetic structure with the Ru spin moments ordered antiferromagnetically along the b axis. We have investigated the resonant inelastic x-ray scattering (RIXS) spectra at the Ru and Ca K, L3, and M3 edges as well as at the OK edge. The experimentally measured RIXS spectrum of Ca3Ru2O7 at the Ru L3 edge possesses a sharp feature ≤2eV corresponding to transitions within the Ru t2g levels. The excitation located from 2 to 4 eV is due to t2g→ eg transitions. The third wide structure situated at 4.5−11eV appears due to transitions between the Ru 4dO states derived from the tails of oxygen 2p states and eg and t2g states. The RIXS spectra at the Ru L3 and M3 edges are quite similar. However, the corresponding RIXS spectra at the Ca site are quite different from each other due to the significant difference in the widths of core levels. The RIXS spectrum at the OK edge consists of three major inelastic excitations. We found that the first two low energy features ≤2.5eV are due to interband transitions between occupied and empty Ot2g states which appear due to the strong hybridization between oxygen 2p and Ru t2g states in close vicinity to the Fermi level. The next major peak between 2.5 and 8 eV reflects interband transitions from occupied O2p to empty Ot2g states. A wide energy interval between 4 and 11 eV is occupied by rather weak O2p→Oeg transitions. Published by the American Physical Society 2024

Electronic structure and resonant inelastic x-ray scattering in the mixed [formula omitted]-[formula omitted] transition-metal oxides Sr[formula omitted]CuIrO[formula omitted], Sr[formula omitted]CuPtO[formula omitted], and Sr[formula omitted]ZnIrO[formula omitted

We have investigated the electronic and magnetic properties of one-dimensional Sr3CuIrO6, Sr3ZnIrO6, and Sr3CuPtO6 oxides within the density-functional theory (DFT) using the generalized gradient approximation while taking into account strong Coulomb correlations (GGA+U) in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. The strong spin–orbit coupling (SOC) in these oxides splits the t2g-type manifold into a lower jeff = 3/2 quartet and an upper jeff = 1/2 doublet. The jeff = 1/2 band is almost completely given by linear combinations of d5/2 states. The occupied jeff = 3/2 band is dominated by d3/2 states with some weight of d5/2 states. We have investigated theoretically the resonant inelastic x-ray scattering (RIXS) spectra at the Ir and Pt L3 edges in Sr3CuIrO6, Sr3ZnIrO6, and Sr3CuPtO6. The experimentally measured RIXS spectrum of Sr3CuIrO6 possesses a sharp feature below 1.3 eV corresponding to transitions within the Ir t2g levels. The excitation located from 3 eV to 5 eV is due to t2g→eg transitions. The next two high energy structures appear due to d−d transitions between the charge transfer Ir 5dct states and t2g and eg states. The theoretically calculated RIXS spectra of Sr3ZnIrO6 and Sr3CuIrO6 at the Ir L3 edges are very similar due to the similarity of their energy band structures. The RIXS spectrum at the Pt L3 edge of Sr3CuPtO6 significantly differs from the corresponding spectra at the Ir L3 edge of Sr3CuIrO6 and Sr3ZnIrO6. There are not any intra-t2g transitions in Sr3CuPtO6 due to fully occupied t2g states. Besides, there are additional 5dCu→eg transitions, where the 5dCu states are derived from the tails of the Cu 3d states inside the Pt atomic spheres.

A new study of the optical and structural characterization properties of p-type ZnS2 pyrite with an application in solar energy

Abstract In this manuscript, we study the grouping of bands and optical properties of p-type Zn S 2 pyrite, which helps us in the study of crystal p-type Zn S 2 pyrite and its impact in organic photovoltaic cells. Our work has two approaches one theorical where we find the band structure of p − type Zn S 2 by using linear muffin-tin orbital method in the atomic-sphere approximation (LMTO-ASA), the second approach is the experimental where we prepare the crystals by chemical vapor transport. The sample was examined by XRD and optical characterizations. Our results show that the p-type Zn S 2 pyrite is a direct semiconductor with optical gap about 1.610 eV and calculated gap about 1.550 eV . As an illustration of our finding, we present an application of our work to photovoltaic devices.

Electronic structure and resonant inelastic x-ray scattering in GaTa4Se8

We have investigated the electronic structure of the lacunar spinel compound GaTa4Se8 within the density-functional theory (DFT) using the generalized gradient approximation while taking into account strong Coulomb correlations (GGA+U) in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. GaTa4Se8 can be classified as a Mott insulator since it was expected to be metallic from GGA band structure calculations in contradiction with the resistivity and optical measurements. Strong SOC splits the t2g-type manifold into a lower jeff = 3/2 quartet and an upper jeff = 1/2 doublet. The empty jeff = 1/2 band is well separated from the jeff = 3/2 one and almost completely given by linear combinations of d5/2 states. The partly filled jeff = 3/2 band is dominated by d3/2 states with some weight of d5/2 ones and consists of two groups of bands separated by an energy gap. The low energy jeff = 3/2 band situated at the Fermi level is very narrow, therefore even a small Hubbard U opens the energy gap. We have investigated theoretically the resonant inelastic x-ray scattering (RIXS) spectra at the Ta L2,3 edges. The calculated results are in good agreement with experimental data. We have found that the best agreement between the theory and experiment in the value of the Hubbard energy gap and RIXS spectra at the Ta L2,3 edges can be achieved for Ueff = 1.0 eV. The experimentally measured RIXS spectrum of GaTa4Se8 at the Ta L3 edge in addition to the elastic scattering peak at 0 eV possesses a sharp feature below 1 eV corresponding to transitions within the Ta t2g levels. The excitation located from 1 eV to 2 eV is due to t2g→eg transitions. The third wide very intensive structure from 2.8 eV up to 12 eV is almost completely derived from ligand-to-ligand charge transfer excitations. Such a situation is quite unique for the RIXS spectra in transition 5d metal systems. The origin of this dominant contribution as well as the electronic correlation in GaTa4Se8 is a consequence of its peculiar crystal structure which forms tetrahedral Ta4 clusters with very small intracluster Ta–Ta and Ta–Se distances and rather large distances between the Ta4 clusters. It results in the formation of localized electronic states and extremely strong Ta 5d - Se 4p hybridization which creates 5dSe states with high density of states. Such hybridization is much stronger in comparison with the corresponding 5d - O 2p hybridization in 5d transition metal oxides due to more extended Se 4p wave functions in comparison with oxygen 2p ones.

Impact of zinc structural on the photovoltaic Properties of iron Pyrite

FeS2 pyrite is one of the most interesting photovoltaic materials with low-cost and natural abundance but with small band gap of 0.95 eV. In the present work, we show the feasibility of increases band gap was determined by Zinc alloying of Iron pyrite. We showed that we can increase the band gap of FeS2 pyrite to 1.15eV by theoretical calculation and to 1.16eV using experimental method, by just adding a very small amount of Zinc (1%). We prepared our samples by chemical vapor transport technic and we utilized the technic of linear muffin-tin orbital method in the atomic-sphere approximation (LMTO-ASA). The effect of Zinc alloyed Iron pyrite were examined by transmission electron micrograph TEM, XRD, Raman spectroscopy and optical characterization.

Electronic structure and x-ray magnetic circular dichroism in cr-doped topological insulator bi2se3

We have studied the structural, electronic, and magnetic properties of the Cr-doped topological insulator Bi2Se3 within the density functional theory using the generalized gradient approximation in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. The X-ray absorption spectra and X-ray magnetic circular dichroism at the Cr K and L2,3 edges have been investigated theoretically from the first principles. The calculated results are in good agreement with the experimental data. The complex fine structure of the Cr L2,3 X-ray absorption spectra in Cr-doped Bi2Se3 has been found to be not compatible with a Cr2+ valency state. Its interpretation demands a mixed valent state.

Electronic structure and X-ray magnetic circular dichroism in the MAX phases T2AlC (T = Ti and Cr) from first principles

We study the electronic and magnetic properties of T2AlC (T = Ti and Cr) compounds in the density-functional theory using the generalized gradient approximation (GGA) with consideration of strong Coulomb correlations (GGA+U) in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital (LMTO) band-structure method. The X-ray absorption spectra and X-ray magnetic circular dichroism (XMCD) at the Cr L2,3 and Cr, Ti, and C K edges were investigated theoretically. The calculated results are in good agreement with experimental data. The effect of the electric quadrupole E2 and magnetic dipole M1 transitions at the Cr K edge has been investigated.

An Insight of the Theoretical Physics of Ru-Alloyed Iron Pyrite Studied for Energy Generation

Pyrite FeS2 has become the focus of many researchers in thin-film photovoltaics because it has some possibilities in photovoltaics. In this manuscript, we present an experimental and a theoretical study of the electronic structure of pyrite FeS2 alloyed with a small concentration of 1.19% of ruthenium (Fe0.9881Ru0.0119S2) by using the Linear Muffin-Tin Orbital Method in the Atomic-Sphere approximation (LMTO-ASA) calculations and the density of states. We observed that the bandgap of FeS2 increases from 0.90508 to 1.21586 eV when we replace ~1.19% of the Fe atoms with ruthenium atoms x=0.0119 concentration of Ru. We prove that this low concentration of Ru saved the gap states and the electronic and optical properties of FeS2 pyrite. Our calculated electronic bandgap is 1.21586 eV and direct. Our results confirm that the symmetric operation of the space Th6 Pa3 saves electronic structure of iron pyrite when alloyed with ruthenium.

First-Principles Calculation of Transport Properties of Heusler Alloy Co2MnAl at Finite Temperatures

We develop a framework for first-principles calculations of the transport properties of magnetic materials at finite temperatures within the coherent potential approximation. First, we calculate the grand potential by the tight-binding linearized muffin-tin orbital method and apply it to the Kubo formula to obtain the temperature dependence of the conductivities. Next, we demonstrate the computation for the magnetic moments M(T), longitudinal and transverse electrical conductivities, σxx(T), σxy(T), Seebeck coefficients Sxx(T), and anomalous Nernst coefficients Nxy(T) of Co2MnAl of both L21 and B2 structures. It is found that σxx(T) of L21 and B2 structures exhibit slow relaxation with temperature compared with most transition metal alloys, which reflects a transition of the system from a half-metallic to metallic system with increasing temperature. The σxy(T = 0) of the B2 structure is much smaller than that of the L21 structure, while σxx(T) of the B2 structure exhibits slower relaxation with temperature than the L21 structure. The Sxx(T) and Nxy(T) exhibit nonmonotonic variation in the low temperature region and the values above room temperature are in agreement with the experimental data.

Band structures and pressure dependence of the band gaps of GaN

The linear muffin-tin orbital method is used with the atomic-sphere approximation to study the ground-state properties, band structures and pressure dependence of the band gaps of zincblende GaN. The equilibrium lattice constant calculated is smaller than the experimental value by about 2%. It is found that the fundamental band gap is direct and that the value (3.90 eV) is in good agreement with the experimental value. The linear pressure coefficient for this band gap is much smaller than those for Ga.As and GaP. The total density of states and local density of. states are discussed. Moreover, the band structure (wurtzite) GaN is also studied. It is found that the band gap of wurtzite GaN is smaller than that of zincblende GaN, which agrees well with the experimental results.

Resonant inelastic x-ray scattering in Ca3LiOsO6 from first-principles

We have investigated the electronic and magnetic properties of the transition metal oxide (TMO) Ca3LiOsO6 within the density functional theory (DFT) using the generalized gradient approximation while taking into account strong Coulomb correlations (GGA+U) in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. Ca3LiOsO6 is an insulator and forms the K4CdCl6-type crystal structure with relatively high Néel temperature TN = 117 K. Despite of the large strength of spin–orbit coupling, it has only a small effect on the electronic and magnetic properties of Ca3LiOsO6. We have also investigated theoretically the x-ray absorption spectra (XAS), x-ray magnetic circular dichroism (XMCD) and resonant inelastic x-ray scattering (RIXS) spectra at the Os L3 edge. The experimentally measured RIXS spectrum of Ca3LiOsO6 in addition to the elastic scattering peak at 0 eV possesses a sharp feature below 2 eV corresponding to transitions within the Os t2g levels. The excitation located at 4.5 eV is due to t2g→eg transitions. The third wide structure situated at 6–8 eV appears due to ligand-to-metal charge transfer excitations: d−d transitions to the Os t2g manifold from the Os 5dO states derived from the ”tails” of oxygen 2p states. The high energy structure at 10–11.5 eV is due to Os 5dO→eg interband transitions. At higher energy above 11 eV transitions from the Os 5dO states to the empty Ca 5d states are located. We have investigated the effect of SO coupling, Coulomb correlations and core-hole effect on the energy band structure, XAS, XMCD, and RIXS spectra in Ca3LiOsO6.

Electronic structure and resonant inelastic x-ray scattering in osmates. I. Perovskite NaOsO3

We have investigated the electronic and magnetic properties of the perovskite ${\mathrm{NaOsO}}_{3}$ within density functional theory using the generalized gradient approximation while taking into account strong Coulomb correlations in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. ${\mathrm{NaOsO}}_{3}$ is a G-type AFM Mott insulator which is characterized by AFM spins canted away from the $c$ axis. This magnetic configuration explains the weak ferromagnetism in ${\mathrm{NaOsO}}_{3}$. Despite the large strength of spin-orbit coupling, it has only a small effect on the electronic and magnetic properties of ${\mathrm{NaOsO}}_{3}$. We have also investigated theoretically the resonant inelastic x-ray scattering (RIXS) spectrum at the Os ${L}_{3}$ edge. The experimentally measured RIXS spectrum of ${\mathrm{NaOsO}}_{3}$ in addition to the elastic scattering peak at 0 eV possesses a sharp feature below 2 eV corresponding to transitions within the Os ${t}_{2g}$ levels, a strong intense peak at around 2.8 eV which is from ${t}_{2g}\ensuremath{\rightarrow}{e}_{g}$ transitions, and a wide structure stretching from 6 eV to 12 eV that corresponds to ligand-to-metal charge transfer excitations, d-d transitions to Os ${t}_{2g}$ and ${e}_{g}$ manifolds from the Os 5${d}_{\mathrm{O}}$ states derived from the ``tails'' of oxygen 2$p$ states.

Electronic structure and resonant inelastic x-ray scattering in osmates. II. Pyrochlore Cd2Os2O7

We have investigated the electronic and magnetic properties of the pyrochlore osmate ${\mathrm{Cd}}_{2}{\mathrm{Os}}_{2}{\mathrm{O}}_{7}$ within density functional theory using the generalized gradient approximation with taking into account strong Coulomb correlations in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. ${\mathrm{Cd}}_{2}{\mathrm{Os}}_{2}{\mathrm{O}}_{7}$ is a Mott insulator with all-in-all-out magnetic order. The optical spectra, x-ray absorption spectra, and x-ray magnetic circular dichroism at the Os ${L}_{2,3}$ edges in the pyrochlore osmate ${\mathrm{Cd}}_{2}{\mathrm{Os}}_{2}{\mathrm{O}}_{7}$ have been investigated theoretically from first principles. The calculated results are in good agreement with experimental data. We have also investigated theoretically the resonant inelastic x-ray scattering (RIXS) spectrum at the Os ${L}_{3}$ edge. The experimentally measured RIXS spectrum of ${\mathrm{Cd}}_{2}{\mathrm{Os}}_{2}{\mathrm{O}}_{7}$ in addition to the elastic scattering peak at 0 eV possesses a sharp feature at 0.9 eV corresponding to transitions within the Os ${t}_{2g}$ levels, a strong intense peak at around 4.5 eV which is from ${t}_{2g}\ensuremath{\rightarrow}{e}_{g}$ transitions, and a wide structure stretching from 5.5 eV to 15 eV that corresponds to ligand-to-metal charge transfer excitations.

Atomistic study of stability and new phase transitions of zinc selenide using FP-LMTO-PLW method

By full potential linear muffin-tin orbitals (FP-LMTO-PLW) method, we have studied the phase transitions of ZnSe under high pressures. The local density approximation (LDA) was used for the exchange and correlation energy. The most important result is the prediction of the possibility of four phase transitions from the cubic zincblende (ZnS-B3) to the B81 (NiAs) structure at 8.00 GPa, the second from B3 to the B32 (NaTi) and Bh (WC) structures at above 45 GPa for each one of them, and from B3 to B2 (CsCl) phase at around 31GPa. The first one (ZnS–NiAs) occurring at a lower pressure than the well knownZnS to NaCl transition (found here to be 11.5 GPa).

Experimental and Theoretical Study on the Nonmagnetic Li/Mg Cosubstitution in the Gd5-x(Li/Mg)xGe4 (x = 1.04, 1.17, 1.53) System.

Three Li- and Mg-cosubstituted compounds in the Gd5-x(Li/Mg)xGe4 (x = 1.04(2), 1.17(2), 1.53(2)) system have been successfully prepared by conventional high-temperature reactions. According to powder and single-crystal X-ray diffraction analyses, all three compounds adopt a Gd5Si4-type phase with the orthorhombic Pnma space group (Pearson code oP16, Z = 4) and six crystallographically independent atomic sites. The crystal structure can be described as a combination of two-dimensional Mo2FeB2-type ∞2[Gd2(Li/Mg)Ge2] layers and [Ge2] dimers. Interestingly, as 64% of Li and 26% of Gd at the RE3 and RE2 sites, respectively, were exclusively substituted by Mg in Gd3.47(1)Li0.36(2)Mg1.17(3)Ge4, the lattice parameter b was selectively shortened as a result of the RE3-Ge1 bond shrinkage in comparison to that in Gd4LiGe4, while lattice parameters a and c remained nearly intact. A series of theoretical calculations using the tight-binding linear muffin-tin orbital (TB-LMTO) method indicated that the reduction of the particular RE3-Ge1 bond distance in the title compounds could also be explained by an optimization of bonding based on the corresponding RE3-Ge1 crystal orbital Hamilton population (COHP) curve. Moreover, the specific site preference of Mg for the RE3 site was supported by both size-factor as well as electronic-factor criteria on the basis of the smallest atomic size and the highest electronegativity of Mg among the three cations. Therefore, the overall electronic structure was further interrogated by a density of states (DOS) analysis. The influence of nonmagnetic Li/Mg cosubstitution for the magnetic Gd atoms in the title Gd5-x(Li/Mg)xGe4 system on the magnetic characteristics was also thoroughly studied by isofield magnetization at 100 Oe and 10 kOe and isothermal magnetization measurements at 4 K using two of the title compounds: Gd3.83(1)Li0.48Mg0.69(3)Ge4 and Gd3.47(1)Li0.36(2)Mg1.17(3)Ge4.

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.

First-principles calculations for Gilbert damping constant at finite temperature

We propose a first-principles calculation method for the Gilbert damping constants α at finite temperature. α is described by the torque correlation model in which the electronic structure is computed by the tight-binding linear muffin-tin orbital method. We include the finite-temperature effect as the transverse spin fluctuation in the disordered local moment picture within the coherent potential approximation. Applying the present method to bcc-Fe and L10-FePt, we demonstrate this temperature-dependent α. By comparing our calculated results with experimental results, we find the calculated values are less than half of the experimental values, reflecting the characteristics of the torque correlation model.

Resonant inelastic x-ray scattering spectra in the hyperhoneycomb iridate β−Li2IrO3 : First-principles calculations

We studied the electronic structure of the $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}$ insulator within the density-functional theory using the generalized gradient approximation while taking into account strong Coulomb correlations in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band structure method. The $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}$ undergoes a pressure-induced structural and magnetic phase transition at ${P}_{c}\phantom{\rule{4pt}{0ex}}\ensuremath{\sim}4$ GPa with symmetry lowering to the monoclinic $C2/c$. The structural phase transition is accompanied by the formation of ${\mathrm{Ir}}_{2}$ dimers on the zigzag chains, with an Ir-Ir distance of $\ensuremath{\sim}2.66$ \AA{}, even shorter than that of metallic Ir. The strong dimerization stabilizes the bonding molecular-orbital state, leads to the collapse of the magnetism, and opens the energy gap with a concomitant electronic phase transition from a Mott insulator to band insulator. The resonant inelastic x-ray scattering spectra (RIXS) at the Ir ${L}_{3}$ edge were investigated theoretically from first principles. The calculated results are in good agreement with the experimental data. We show that the drastic reconstruction of the RIXS spectral peak at 0.7 eV associated with the structural $Fddd\ensuremath{\rightarrow}C2/c$ phase transition at ${P}_{c}$ can be related to the disappearing of the Coulomb correlations in the high-pressure $C2/c$ phase.