Energy Band Method Research Articles

Effect of the mechanical strength on the ion transport in a transition metal lithium halide electrolyte: first-principle calculations

The transition metal lithium halides (such as Li 3 InCl 6 , Li 3 ScCl 6 and Li 3 ErBr 6 ) have high ionic conductivity and good stability with air that can be used as solid electrolyte. However, the effect of mechanical strength on ion transport cannot be ignored in transition metal lithium halides. The relationship between the ion transport and mechanical strength of the transition metal lithium halide solid electrolyte were investigated by the first-principle based density functional theory. The bulk structure was optimized, the mechanical properties and ion transport of the solid electrolyte were analyzed, and the mechanical constants and ideal strength were calculated. The elastic energy band (NEB) method was used to simulate the diffusion of lithium ions in the bulk phase. The results show that Li 3 InCl 6 , Li 3 ScCl 6 and Li 3 ErBr 6 have better ductility, as their bulk shear modulus ratios are all greater than 1.75. The Li 3 ScCl 6 inorganic solid electrolyte with higher shear modulus (7.568 GPa) and tensile stress (3.0885 GPa) is more favorable for inhibiting the growth of lithium dendrites. The Li 3 ScCl 6 has a lower migration energy barrier along the O-T-O channel than that of Li 3 ScCl 6 and Li 3 ErBr 6 in the bulk structure. The energy barrier for lithium ion migration has changed in the channel of the solid electrolyte due to the effect of mechanical strength. The lattice distortion will affect the transport of lithium ions. These results provide comprehensive insights into the practical application of these halides as solid electrolytes. • The mechanics and transport of solid electrolyte are coupled to calculate. • The channel bottleneck of lattice distortion affects transport energy barrier. • The mechanical strength of SSEs inhibits the longitudinal growth of dendrites.

Atomistic full-quantum transport model for zigzag graphene nanoribbon-based structures: Complex energy-band method

Using a non-equilibrium Green’s function framework in combination with the complex energy-band method, an atomistic full-quantum model for solving quantum transport problems for a zigzag-edge graphene nanoribbon (zGNR) structure is proposed. For transport calculations, the mathematical expressions from the theory for zGNR-based device structures are derived in detail. The transport properties of zGNR-based devices are calculated and studied in detail using the proposed method.

Structural stability and stabilization of Li2MoO3.

Due to its better physical and electrochemical properties, Li2MoO3 was proposed to replace Li2MnO3 for constructing new Li-rich cathode materials. However, the molybdenum (Mo)-ion shuttling between the Li layer and the Mo layer upon electrochemical Li-extraction raises concerns on the structural stability of the Mo-based Li-rich materials. In this article, the nudged energy band method was applied using first-principles calculations to understand the reason for the Mo-ion migration and to sieve substituent elements for Mo from a number of transition metals. Molecular dynamics calculations were performed to simulate the kinetic properties of the pristine and transition metal substituted Li2MoO3. On the basis of these calculations, antimony (Sb) was proposed as a substituent to enhance the structural stability of Li2MoO3 and improve its rate performance.

Systematic Theoretical Investigation for Adsorption Behavior of CO on β-SiC (001) Surface

Based on the first-principles pseudopotentials and the plane wave energy band method, the adsorption behaviors of CO molecules on β-SiC (001) surfaces have been investigated in this paper. The calculations for stable adsorption site demonstrate that CO molecule is adsorbed at the lattice site of β-SiC. The absorbing energy of CO on SiC (001) surface is 2.984eV while the exclusion energy between CO reaches 2.965eV. The densities of State of CO became wider and it extends to lower energy when they adsorbent atβ-SiC (001) surfaces.

First-principles calculation on the concentration of intrinsic defects in 4H-SiC

Based on the first-principles pseudopotentials and the plane wave energy band method, the supercells of perfect crystal 4H-SiC and those with intrinsic defects VC, VSi, VC—C and VC—Si were calculated. Ignoring the atomic relaxations, the results show that the formation energy of intrinsic defects is ranked, from low to high, as VC, VC—C, VSi to VSi—Si at 0 K. The equilibrium concentration of each intrinsic defect can be deduced from the formation energy of each intrinsic defect. The concentration ranks, from high to low, as VC, VC—C, VSi, VSi—Si, which is in accordance with the ESR and PL results. The stabilizing process of metastable defects VSi converting to VC—C was explained by formation energy.

Ir(001) 위의 철 단층의 자성에 대한 전자구조 연구

Ir(001) 표면 위에 얹혀진 철 단층의 자성을 제일원리 전자구조 계산방법을 이용하여 이론적으로 탐구하였다. 비교를 위하여 Fe와 Ir이 규칙적으로 반반 섞인 위층에 대하여도 계산하였다. 모두 Fe로 이루어진 단층의 경우 철원자의 자기모멘트는 2.95 보어마그네톤으로 비교적 큰 값을 가졌으며, Fe와 Ir이 반반 섞인 위층에서 Fe의 자기모멘트는 2.83 보어마그네톤이었다. 이러한 자성과 전자구조의 자세한 면은 계산된 상태밀도와 스핀밀도를 통하여 논의한다. 각 위층 원자의 평형위치를 구하기 위해 총에너지와 원자힘 계산을 하였다. 그 결과 Fe 위층에서의 Fe 원자위치가 Fe와 Ir이 반반 섞인 위층의 Fe 위치보다 Ir 기판에 다소 가까웠다. The magnetism of the Fe monolayer on Ir(001) substrate [Fe/Ir(001)] was investigated by the first-principles energy band method. For comparison, the Fe and Ir ordered-alloyed monolayer on Ir(001) [Fe<TEX>$_{0.5}$</TEX>Ir<TEX>$_{0.5}$</TEX>/Ir(001)] was also considered. The calculated magnetic moments for Fe atoms in Fe/Ir(001) system and Fe<TEX>$_{0.5}$</TEX>Ir<TEX>$_{0.5}$</TEX>/Ir(001) system are 2.95 and 2.83 bohr magnetons, respectively. The detailed aspects of the magnetism and electronic structures for these systems are discussed with the calculated denisty of states and spin densities. The optimized atomic sites for the overlayer Fe and Ir atoms were determined by the total energy and atomic force calculations. The Fe atoms in Fe/Ir(001) move closer to the substrate Ir layer than the Fe atoms in Fe<TEX>$_{0.5}$</TEX>Ir<TEX>$_{0.5}$</TEX>/Ir(001) do to the Ir substrate.

Electronic structures and magnetic properties of RB4 (R=Yb,Pr,Gd,Tb,Dy)

Most rare-earth tetraborides RB4 have antiferromagnetic ground states except for YbB4 and PrB4. We have investigated the electronic structures and magnetic properties of RB4 (R=Yb,Pr,Gd,Tb,Dy) employing the first-principles total energy band method. It is found that YbB4 has the paramagnetic ground state, while the other tetraborides are in the magnetic ground state, which is in agreement with experiments. We have obtained the spin and orbital magnetic moments and discussed the importance of the spin-orbit interaction and the on-site Coulomb repulsion (U) in these systems.

페로브스카이트 구조를 가지는 Ti0.96Co0.02Fe0.02O2의 전자구조와 자성

페로브스카이트 구조를 가지는 전이금속 질화물인 <TEX>$FeCo_3N$</TEX>과 <TEX>$NiCo_3N$</TEX>의 전자구조를 전전자 총퍼텐셜선형보강평면파(all electron FLAPW) 방법에 의해 계산하고, 그 결과를 <TEX>$Co_4N$</TEX>의 전자구조와 비교함으로써 꼭지점에 위치한 Co 원자(CoI)를 Fe과 Ni 원자로 대치하였을 때의 영향을 탐구하였다. CoI원자를 각기 Fe와 Ni 원자로 대치한 경우에 면심위치의 CoII 원자의 자기모멘트는 1.458과 <TEX>$1.494\;{\mu}_B$</TEX>으로 대치하지 않은 경우와 비교하여 커다란 차이가 없었다. <TEX>$FeCo_3N$</TEX>과 <TEX>$NiCo_3N$</TEX>에서 꼭지점에 위치한 Fe와 Ni 원자의 자기모멘트는 각기 3.086과 <TEX>$0.795\;{\mu}_B$</TEX>로 거의 포화된 값을 가졌으며, 국소적 자성을 나타냈다. We calculated the electronic structures of substituted cobalt nitrides, that is <TEX>$FeCo_3N$</TEX> and <TEX>$NiCo_3Ni$</TEX>, by using the all electron fullpotential linearized augmented plane-wave (FLAPW) energy band method, and investigated the influence on the magnetic properties of <TEX>$Co_4N$</TEX> due to the substitution of Co atom located at corner sites by iron and nickel atoms. We found that the magnetic moments of CoII atoms located at the face-center positions in these compounds are almost same to that of <TEX>$Co_4N$</TEX>. The magnetic moments of Fe and Ni atoms in <TEX>$FeCo_3N$</TEX> and <TEX>$NiCo_3Ni$</TEX> are 3.086 and <TEX>$0.795\;{\mu}_B$</TEX>, and they have the localized nature of magnetism.

VRu(001) 표면의 자성에 대한 제일원리 연구

CsCl 구조를 가진 VRu(001) 표면의 자기적 성질을 일반기울기근사(GGA)를 채택한 총퍼텐셜선형보강평면파(FLAPW) 에너지 띠 계산 방법을 이용하여 이론적으로 연구하였다. 이를 위해 각기 V 및 Ru 원자층으로 끝나는 두 개의 (001) 표면을 고려하였다. 계산된 머핀-틴 구 내의 다수 및 소수 전자의 수로부터 V로 끝나는 표면의 자기모멘트는 <TEX>$1.71_{{\mu}_B}$</TEX>로 매우 큰 값을 가졌으며, Ru로 끝나는 표면은 자성이 거의 없는 것으로 계산되었다. 이러한 자성을 계산된 스핀분극상태밀도와 스핀전하밀도와 연관지어 설명하였다. We investigated the magnetic properties of VRu(001) surface by using the all electron full-potenial linearized augmented planewave (FLAPW) energy band method within the GGA. We consider two different configurations, V and Ru surface layers, respectively. The V atoms in surface layer was calculated to have large magnetic moment of <TEX>$1.71_{{\mu}_B}$</TEX> while the Ru surface layer to have nearly nonmagnetic state. The calculated spin-polarized density of states. spin density contour, and charge density were discussed in relation to the magnetic properties of VRu(001) surface.

나노 구조 철띠의 자성과 전자구조에 대한 제일원리 연구

나노 구조 철띠의 자기적 성질을 일반기울기 근사(GGA)를 채택한 전전자 full-potenial linearized augmented plane-wave(FLAPW)에너지 띠 방법을 이용하여 이론적으로 연구하였다. 세 줄, 다섯 줄, 일곱 줄의 철선으로 이루어진 띠에서 가장자리 줄의 자기모멘트는 2.97 또는 2.98 <TEX>${\mu}_B$</TEX>로 Fe 단일 직선의 값과 비슷하게 포화된 값을 가졌으며, 가운데 선의 자기모멘트는 2.82 <TEX>${\mu}_B$</TEX>로 2차원 격자의 값과 같았다. 일곱 줄로 이루어진 철 띠의 전하밀도나 스핀밀도는 가장자리 영역에서 거의 평평한 분포를 보였는데, 이는 가장자리 원자로부터 배출된 p-전자로 인한 가리기에 의한 것이다. 일곱 줄로 이루어진 철 띠에서 가장자리 원자의 상태밀도는 가운데 원자에 비해 띠폭이 줄어들었는데 이는 가장자리 효과에 의한 띠좁힘 때문이다. We investigated the magnetic properties of Fe nanostripes by using the all electron full-potenial linearized augmented plane-wave (FLAPW) energy band method within the generalized gradient approximation (GGA). The magnetic moments of the Fe atoms in the edge Fe chains of the stripes composed of three, five, and seven chains have saturated values of 2.97 or 2.98 <TEX>${\mu}_B$</TEX>, and the values of the center chains are 2.82 <TEX>${\mu}_B$</TEX> which is similar to that of 2D square lattice. The charge and spin density contour plots showed that the flat distribution in the edge region of the stripes, and it is due to the spilled out p-electrons from the atoms in the edge line. The calculated density of states for the edge atoms in the stripes with seven Fe chains showed that the narrowed width compared to that of center atoms due to the band narrowing effect at the edge.

Density functional investigation of the electronic structure of cobalt phthalocyanine monolayer

The electronic structure of cobalt phthalocyanine (CoPc) monolayer is investigated by means of the first-principles all-electron full-potential linearized augmented plane wave energy band method. The magnetic properties of the CoPc monolayer are studied with spin polarised calculations. It was found that Co atom has magnetic moment of 1.01 μ B . Charge transfer between the CoPc ligand π and metal atom d orbitals causes a weak polarisation of nitrogen atoms within the molecule inner ring. The electronic properties of Co atom are essential in shaping the ground state electronic structure of the CoPc monolayer near the Fermi level. The calculated values of work function and ionisation potential of the model monolayer are 5.01 and 6.46 eV, respectively.

Electronic structure of copper phthalocyanine monolayer: a first-principles study

The electronic structure of copper phthalocyanine (CuPc) monolayer was investigated by the first-principles all-electron full-potential linearized augmented plane wave (FLAPW) energy band method. The magnetic properties of the CuPc monolayer were investigated with spin-polarized calculation. It was found that the Cu atom has a magnetic moment of 0.56 μ B, but it does not affect strongly the paramagnetic properties of the monolayer. The ground-state electronic structure of the CuPc monolayer found in spin-polarized calculation is indistinguishable from the paramagnetic case in the energy range from −10 to −1.5 eV and above 1.0 eV, with respect to the Fermi level ( E F), but taking into account the magnetic properties of the open-shell Cu atom results with the splitting of bands near E F . The obtained total density of states and the calculated values of work function (4.66 eV) and ionization potential (5.23 eV) of the CuPc monolayer were found to be in a good agreement with the experimental data concerned CuPc thin films.

First-principles study on the electronic structures of iron phthalocyanine monolayer

The electronic band structure and magnetic properties of iron phthalocyanine (FePc) monolayer were investigated by using the first-principles all-electron full-potential linearized augmented plane wave energy band method. It is found that the ferromagnetic FePc monolayer is energetically more stable than the paramagnetic one. The exchange interaction, which splits the majority and minority bands, influences strongly on the electronic structure near the Fermi level ( E F). Magnetic moment of the central Fe atom is calculated to 1.95 μ B. The range of the positive polarization of Fe site is larger in the out-of-plane than in the in-plane direction. The FePc ligand remains paramagnetic. The presence of states at E F indicates the metallic character of FePc monolayer both for the paramagnetic and ferromagnetic states. However, the large density of states at E F of the majority spins in the ferromagnetic state is expected to cause a phase transition to insulating antiferromagnetic state from the metallic ferromagnetic one.

First-principles calculation of the vacancy formation energies in LiAl

The LiAl is a typical intermetallic compound which has many important applications. We have employed the first-principles pseudopotentials and the plane wave energy band method to calculate the vacancy formation energies of Li and Al vacancies in LiAl intermetallic compound as well as the atomic relaxations around the vacancies. The charge redistribution around the vacancies, electronic densi ty of states and their band structures are also discussed.

Ab initio study of the electronic structure of nickel phthalocyanine—monolayer and bulk

The electronic structure of nickel phthalocyanine (NiPc) monolayer and bulk was investigated by means of the first-principles all-electron full-potential linearized augmented plane-wave (FLAPW) energy band method. The calculated electronic band structure of bulk was found to be similar to that of monolayer, especially from −3.2 eV to the Fermi level ( E F). The bands close to the E F are mostly contributed from the nickel d states. Some difference in the electronic structures between monolayer and bulk was found in the energy range from −8 to −3 eV and 2 eV above the E F. The analysis of the obtained results was consistent with the data obtained through the molecular orbital energy levels calculation provided for an isolated NiPc molecule with the Hartree–Fock (HF) self-consistent field method.

Simulation Studies of Electronic Properties and Atomic Ordering in the b-Si 3 N 4 – Mg – O SYSTEM

Simulation studies of the electronic structure, interatomic bonds, chemical composition, and atomic ordering in solid solutions Si6–x MgxO2x N8–2x of the β-Si3N4 – Mg – O system and solid solutions Si6–x MgxOxN8–2x Xx (X = S, Se) and Si6–x Mg x/2M x/2OxN8–x (M = C, Si, Ti, Ge, Zr, Sn, and Pb) are carried out using the strong-coupling energy-band method. Stabilization of solid solutions Si6–x MgxO2x N8–2x is accomplished in the presence of S, Se or Zr. In these solutions, Mg and O atoms are capable of forming quasi-unidimensional structures (dopant, or impurity, channels) similar to those predicted for β-sialons.

Surface and interface magnetism of Fe/Cr/Fe[001

The surface and interface magnetism of Fe/Cr/Fe(001) is investigated using the full-potential linearized augmented-plane-wave (FLAP W) energy band method. It is found that the magnetic moment of surface Fe is 2.37 &#x003BC;_B which is smaller than that of clean bcc Fe surface (2.98 &#x003BC;<sub<B</sub>) but larger than that of bulk Fe (2.22 &#x003BC;_B). The calculated magnetic moment of interface Fe, 2.01 &#x003BC;_B, is smaller than that of bulk value, while that of interface Cr, 0.75 &#x003BC;_B, is slightly enhanced compared with the bulk value (0.59 &#x003BC;_B). We find that these features are related to a strong d-d hybridization between Fe and Cr. We also compare our results with previous calculations of Fe/Cr(001). The calculated charge density, spin density, and density of states are presented and discussed in relation to magnetic properties.

Modeling the properties of quartz with clusters

We illustrate a cluster approach to calculate the electronic properties of α-quartz. Cluster approaches to modeling defects and other localized states within crystalline matter have a number of computational advantages when compared to traditional energy band methods. However, the implementation of cluster models has been inhibited by the poor convergence of bulk properties with cluster size. Here we illustrate recent developments in algorithm construction which allow one to consider larger clusters than previously accessible. In particular, we use clusters such as Si 18O 23H 26 and Si 25O 34H 32 to model quartz. We compare these cluster calculations to plane-wave-pseudopotential calculations for crystalline quartz and find very good agreement.

Local spin-density theory of interface and surface magnetocrystalline anisotropy: Pd/Co/Pd(001) and Cu/Co/Cu(001) sandwiches

The interface magnetocrystalline anisotropy (MCA) of Cu/Co/Cu(001) and Pd/Co/Pd(001) sandwiches are investigated, employing our recently developed state tracking approach based on the full potential linearized augmented plane wave energy band method. The strong negative MCA energy for the Co monolayer is found to be decreased for Co/Cu, and even becomes positive for Co/Pd due to the interfacial hybridization, which reduces the spin orbit coupling (SOC) between the dxz,yz − dz2 pair at M̄.

Validity and the applicablity of magnetic-circular-dichroism sum rules for transition metals (invited)

X-ray magnetic-circular-dichroism (MCD) spectra are calculated using the thin film full potential linearized augmented plane wave energy band method for transition metal surfaces. Together with a model analysis, a clear physical insight is provided for this new and exciting phenomenon. The MCD sum rule for the orbital moments originally derived from a single ion model are found to be valid to within 5–10% even in the band approach which treats the strongly hybridized multiband structure. However, the spin sum rule may result in a larger error due to the effects of s,p−d hybridization. In addition, the magnetic dipole term is very important in the spin sum rule, especially for atoms with lower local symmetry.