Effect of strain on structure and electronic properties of monolayer C_(4)N_(4)

The first-principles calculations are performed to examine structural,mechanical,and electronic properties at large strain for a monolayer C_(4)N_(4),which has been predicted as an anchoring promising material to attenuate shuttle effect in Li–S batteries stemming from its large absorption energy and low diffusion energy barrier.Our results show that the ideal strengths of C_(4)N_(4)under tension and pure shear deformation conditions reach 13.9 GPa and 12.5 GPa when the strains are 0.07 and 0.28,respectively.The folded five-membered rings and diverse bonding modes between carbon and nitrogen atoms enhance the ability to resist plastic deformation of C_(4)N_(4).The orderly bond-rearranging behaviors under the weak tensile loading path along the[100]direction cause the impressive semiconductor–metal transition and inverse semiconductor–metal transition.The present results enrich the knowledge of the structure and electronic properties of C_(4)N_(4)under deformations and shed light on exploring other two-dimensional materials under diverse loading conditions.

Density functional theory study of influence of impurity on electronic properties and reactivity of pyrite

The electronic property of pyrite supercell containing As,Se,Te,Co or Ni hetero atoms were calculated using density functional theory（DFT）,and the reactivities of pyrite with oxygen and xanthate were discussed by frontier orbital methods.The cell volume expands due to the presence of impurity.Co and Ni mainly affect the bands near Fermi levels,while As mainly affects the shallow and deep valence bands,and Se and Te mainly affect the deep valence bands.Electronic density analysis suggests that there exists a strong covalent interaction between hetero atom and its surrounding atoms.By frontier orbital calculation,it is suggested that As,Co and Ni have greater influence on the HOMO and LUMO of pyrite than Se and Te.In addition,pyrite containing As,Co or Ni is easier to oxidize by oxygen than pyrite containing Se or Te,and pyrite containing Co or Ni has greater interaction with collector.These are in agreement with the observed pyrite practice.

First-principles study of phase stability and electronic properties of RhZr

First-principles calculations were carried out to investigate the structural stabilities and electronic properties of RhZr.The plane wave based pseudopotential method was used,in which both the local density approximation（LDA） and the generalized gradient approximation（GGA） implanted in the CASTEP code were employed.The internal positions of atoms in the unit cell were optimized and the ground state properties such as lattice parameter,density of state,cohesive energies and enthalpies of formation of ortho-RhZr and cubic-RhZr were calculated.The calculation results indicate that ortho-RhZr can form more easily than cubic-RhZr and the ortho-RhZr is more stable than cubic-RhZr.The density of states（DOS） reveals that the strong bonding in the Rh-Zr and Rh-Rh or Zr-Zr interaction chains accounts for the structural stability of ortho-RhZr and the hybridization between Rh-4d states and Zr-4d states is strong.

First-principles calculation of electronic properties of N-and X(X=S,Se,Te)-codoped anatase TiO_2

The impact of N-and X（X=S,Se,Te）-codoping on electronic properties of anatase TiO2 has been systematically investigated using density functional theory （DFT）.The optimized geometry shows that there is large lattice expansion for the codoped anatase TiO2 due to large atomic radius of the codoped atom.The calculated substitution energies indicate that incorporation of X（X =S,Se,Te） into N-doped bulk TiO2 can not promote synergistic effect on N after substituting for Ti,whcreas it is bctter after substituting for O.According to the total density of states （DOS） and corresponding partial DOS （PDOS）,it can be seen that substituting X（X =S,Se,Te） for O,N 2p orbital is strongly hybridized with impurity states （S 3p,Se 4p,Te 5p）.After substituting X（X=S,Se,Te） for Ti,conduction band is mainly dominated by Ti 3d orbit and S 3p （Se 4p or Te 5p）-N 2p-Ti 3d hybridized states are formed.Based on Bader analysis,it can be indicated that the electron transfer is from N to X（X=S,Se,Te） if substituting X（X=S,Se,Te） for O,but it is opposite if substitute X（X=S,Se,Te） for Ti.

Electronic properties of graphene nanoribbon doped by boron/nitrogen pair:a first-principles study

By using the first-principles calculations, the electronic properties of graphene nanoribbon （GNR） doped by boron/nitrogen （B/N） bonded pair are investigated. It is found that B/N bonded pair tends to be doped at the edges of GNR and B/N pair doping in GNR is easier to carry out than single B doping and unbonded B/N co-doping in GNR. The electronic structure of GNR doped by B/N pair is very sensitive to doping site besides the ribbon width and chirality. Moreover, B/N pair doping can selectively adjust the energy gap of armchair GNR and can induce the semimetal-semiconductor transmission for zigzag GNR. This fact may lead to a possible method for energy band engineering of GNRs and benefit the design of graphene electronic device.

Phase transition, elastic and electronic properties of topological insulator Sb_2Te_3 under pressure: First principle study

The phase transition, elastic and electronic properties of three phases（phase Ⅰ,Ⅱ, and Ⅲ） of Sb_2Te_3 are investigated by using the generalized gradient approximation（GGA） with the PBESOL exchange–correlation functional in the framework of density-functional theory. Some basic physical parameters, such as lattice constants, bulk modulus, shear modulus,Young＇s modulus, Poisson＇s ratio, acoustic velocity, and Debye temperature Θ are calculated. The obtained lattice parameters under various pressures are consistent with experimental data. Phase transition pressures are 9.4 GPa（Ⅰ→Ⅱ） and 14.1 GPa（Ⅱ→Ⅲ）, which are in agreement with the experimental results. According to calculated elastic constants, we also discuss the ductile or brittle characters and elastic anisotropies of three phases. Phases Ⅰ and Ⅲ are brittle, while phaseⅡ is ductile. Of the three phases, phaseⅡ has the most serious degree of elastic anisotropy and phase Ⅲ has the slightest one.Finally, we investigate the partial densities of states（PDOSs） of three phases and find that the three phases possess some covalent features.

First-principles investigation of N-Ag co-doping effect on electronic properties in p-type ZnO

The geometric structure, band structure and density of states of pure, Ag-doped, N-doped, and N-Ag codoped wurtzite ZnO have been investigated by the first-principles ultra-soft pseudopotential method based on the density functional theory. The calculated results show that the carrier concentration is increased in the ZnO crystal codoped by N and Ag, and the codoped structure is stable and is more in favour of the formation of p-type ZnO.

Ground state parameters,electronic properties and elastic constants of CaMg3:DFT study

The present study aims to investigate the equation of state(EOS)parameters of CaMg3 in aReCh(D09),AIFR(DO3),CU3A11(LI2)and CuTi3(L60)structures,using full potential linear muffin-tin orbitals(FP-LMTO)approach based on the density functional theory(DFT).The local density approximation(LDA)and the generalized gradient approximation(GGA)were both applied for the exchange-correlation potential term.The calculated equation of slate parameters at equilibrium,in general,agreed well with the available data of the literature.The calculations showed that under compression CaMg3 transforms from DO3 to DO9 at about 29.96GPa,and 25.1 GPa using LDA and GGA,respectively.The elastic constants C,y,aggregate moduli,Vickers hardness,sound velocity,and Debye temperature of CaMg3 in D03 structure were also reported,discussed and analyzed.Using LDA(GGA),the calculated values of Hv andθD were found at around 5.80GPa(5.93GPa)and 393.44 K(389.91 K),respectively.Electronic band structure,total density of states(TDOS)as well as the partial density of states(PDOS)have been also obtained.The electronic band structure confirms the metallic behavior of CaMg3 in DO3 phase,the valence bands are dominated by the maximum contribution of‘d’like states of Ca in the energy ranging from 2 to 3 eV for GGA,and from 4.5 to 5 eV for LDA,respectively.

Geometrical Structures and Electronic Properties of Copper-Doped Aluminum Clusters

Using density function theory （DFT）, the Cu-doped Aln （n=1-15） clusters have been stud- ied. The electron affinity, ionization potential, Mulliken population analysis of Cu, mean polarizability, polarizability anisotropy, dipole moments and HOMO-LUMO gaps have also been calculated on the basis of optimized geometries. The results indicate that there is magic numbers in copper-doped aluminum clusters and electronic characteristic depended on the size of clusters. As n=13, the electron affinity and ionization potential of cluster changed more than 0.3 and 0.6 eV respectively, compared with neighborhood clusters.

Structural, elastic and electronic properties of Cu-X compounds from first-principles calculations

The structural, elastic and electronic properties of Cu-X compounds in the Cu-X(X =Al, Be, Mg, Sn, Zn and Zr) systems were predicted systematically by first-principles calculations. The ground state properties such as lattice constant, bulk modulus(B)and it's pressure derivative(B') were predicted by fitting a four-parameter Birch–Murnaghan equation and the elastic constants(cij′s)are determined by an efficient strain-stress method. The calculated lattice parameters and cij′s of these binary compounds agree well with the available experimental data in the literature. In addition, elastic properties of polycrystalline aggregates including bulk modulus(B), shear modulus(G), elastic modulus(E), B/G(bulk/shear) ratio, and anisotropy ratio(AU) are calculated and compared with the experimental and theoretical results available in the literature. Based on electronic density of states(DOS) analysis, it can be revealed that all the compounds in the present work are metallic in nature.

Effects of Eu_2O_3 doping on microstructural and electronic properties of ZnO Bi_2O_3-based varistor ceramics prepared by high-energy ball milling

ZnO-Bi2O3-based varistor ceramics doped with EU2O3 in a range from 0 to 0.4% were obtained by high-energy ball milling and fired at 900-1000 ℃ for 2 h. XRD and SEM were applied to determine the phases and microstructure of the varistor ceramics. A DC parameter instrument was applied to investigate the electronic properties and V-I characteristics. The XRD analysis of Eu2O3-doped ZnO-Bi2O3-based varistor ceramics shows that the ZnO, Eu-containing Bi-rich, Zn7Sb2O12-type spinel and Zn2Bi3Sb3O14-type which is the pyrochlore phase are present. With increasing Eu2O3 content, the average size of ZnO grain firstly decreases and then increases. The grain boundary defect model was particularly used to explain the excellent nonlinearity of ZnO-Bi2O3-based varistor ceramics with the addition of0.1% Eu2O3 and sintered at 950 ℃.

Calculated Structure,Elastic and Electronic Properties of Mg_2Pb at High Pressure

The effects of high pressure on structure, elastic and electronic properties of the intermetallic MgzPb were calculated by the first-principles plane wave pseudo-potential method in the scheme of density functional theory （DFT） within the generalized gradient approximation. The elastic constants and Debye temperature obtained at 0 GPa are in good agreement with the available experiment data and other theoretical results. The electronic properties calculated suggest that the electronic density of states （DOS） at the Fermi level decreases under high pressure.

Electronic properties of hydrogen- and oxygen-terminated diamond surfaces exposed to the air

The electronic properties of hydrogen- and oxygen-terminated diamond surfaces exposed to the air are investigated by scanning probe microscopy （SPM）. The results indicate that for the hydrogen-terminated diamond surface a shallow acceptor above the valence-band-maximum （VBM） appears in the band gap. However, the oxygen-terminated diamond film exhibits a high resistivity with a wide band gap. Based on the density-functional-theory, the densities of states, corresponding to molecular adsorbate in hydrogenated and oxygenated diamond （100） surfaces, are studied. The results show that the shallow acceptor in the band gap for the hydrogen-terminated diamond film can be attributed to the interaction between the surface C H bonding orbitals and the adsorbate molecules, while for the oxygen-terminated diamond film, the interaction between the surface C-O bonding orbitals and the adsorbate molecules can induce occupied states in the valence-band.

Assessing the effect of hydrogen on the electronic properties of 4H-SiC

As a common impurity in 4 H silicon carbide(4 H-Si C),hydrogen(H)may play a role in tuning the electronic properties of 4 H-Si C.In this work,we systemically explore the effect of H on the electronic properties of both n-type and p-type4 H-Si C.The passivation of H on intrinsic defects such as carbon vacancies(V_(Si) )and silicon vacancies(V_(Si)) in 4 H-Si C is also evaluated.We find that interstitial H at the bonding center of the Si-C bond(H_(i)^(bc)) and interstitial H at the tetrahedral center of Si(H_(i)^(bc)) dominate the defect configurations of H in p-type and n-type 4 H-Si C,respectively.In n-type 4 H-Si C,the compensation of HSi-te iis found to pin the Fermi energy and hinder the increase of the electron concentration for highly N-doped 4 H-Si C.The compensation of Hbc iis negligible compared to that of V_(Si)on the p-type doping of Al-doped 4 H-Si C.We further examine whether H can passivate VCand improve the carrier lifetime in 4 H-Si C.It turns out that nonequilibrium passivation of VCby H is effective to eliminate the defect states of V_(Si),which enhances the carrier lifetime of moderately doped 4 H-Si C.Regarding the quantum-qubit applications of 4 H-Si C,we find that H can readily passivate V_(Si)during the creation of V_(Si)centers.Thermal annealing is needed to decompose the resulting V_(Si)-n H(n=1-4)complexes and promote the uniformity of the photoluminescence of V_(Si)arrays in 4 H-Si C.The current work may inspire the impurity engineering of H in 4 H-Si C.

Atomic relaxation,stability and electronic properties of Mg2Sn(100)surfaces from ab-initio calculations

Mg2Sn(100)surfaces were investigated using ab-initio method based on density functional theory in order to explore the surface properties.It is found that both the eleven-layers for Mg-termination surfaces and the nine-layers for Sn-termination surfaces are all converged very well.The effects of relaxation mainly occurred within the three outermost atomic layers for both Mg and Sn terminations during the surface relaxation.Mg-termination surfaces are more stable than Sn-termination surfaces according to the analysis of surface energy.The density of states reveals the metallic property of both Mg-termination and Sn-termination surfaces.Covalent bonding exists in Mg2Sn(100)surfaces according to the analysis of partial density of states.

Ab initio investigation of the structural and unusual electronic properties of α-CuSe (klockmannite)

In this article, a computational analysis has been performed on the structural properties and predominantly on the electronic properties of the α-CuSe （klockmannite） using density functional theory. The studies in this work show that the best structural results, in comparison to the experimental values, belong to the PBEsol-GGA and WC-GGA functionals. However, the best results for the bulk modulus and density of states （DOSs） are related to the local density approximation （LDA） functional. Through utilized approaches, the LDA is chosen to investigate the electronic structure. The results of the electronic properties and geometric optimization of α-CuSe respectively show that this compound is conductive and non-magnetic. The curvatures of the energy bands crossing the Fermi level explicitly reveal that major charge carriers in CuSe are holes, whose density is estimated to be 0.86×1022 hole/cm3. In particular, the Fermi surfaces in the first Brillouin zone demonstrate interplane conductivity between （001） planes. Moreover, the charge carriers among them are electrons and holes simultaneously. The conductivity in CuSe is mainly due to the hybridization between the d orbitals of Cu atoms and the p orbitals of Se atoms. The former orbitals have the dual nature of localization and itinerancy.

Kinetic, electronic properties and conductivity studies of （（12Z）N-（5Z）-1-bromo-5-（phenylimino）-1H-pyrrol-2（5H）-ylidene benzenmine {ArN（CNBrCCHCH）NAr} （Ar = C6H5）

Kinetic and conductivity of new Schiff bases compounds such （（12Z）N-（5Z）-1-bromo-5-（phenylimino）-1H- pyrrol-2（5 H）-ylidene）benzenamine {ArN（CNBrCCHCH）NAr} （Ar = C6H5） incorporating the chelating diamino has been studied in this paper and was found a second order of this reaction. Electronic Properties using hyperchem program study has been improved for this compound such angel and bond distance, and then this compound was defining as electric conductivity and did prove to be useful for conduclively compound.

Stability,defect and electronic properties of graphane-like carbon-halogen compounds

We perform first-principles total energy calculations to investigate the stabilities and the electronic structures of graphane-like structures of carbon-halogen compounds, where the hydrogen atoms in the graphane are substituted by halogen atoms. Three halogen elements, fluorine （F）, chlorine （C1） and bromine （Br）, are considered, and the graphane-like structures are named as CF, CC1 and CBr, respectively. It is found that for the single-atom adsorption, only the F adatom can be chemically adsorbed on the graphene. However, the stable graphane-like structures of CF, CC1 and CBr can form due to the interaction between the halogen atoms. The carbon atoms in the stable CF, CC1 and CBr compounds are in the sp3 hybridization, forming a hexagonal network similar to the graphane. The electronic band calculations show that CF and CC1 are semiconductors with band gaps of 3.28 eV and 1.66 eV, respectively, while CBr is a metal. Moreover, the molecular dynamics simulation is employed to clarify the stabilities of CF and CC1. Those two compounds are stable at room temperature. A high temperature （：〉 1200 K） is needed to damage CF, while CC1 is destroyed at 700 K. Furthermore, the effects of a vacancy on the structure and the electronic property of CF are discussed.

Electronic properties of one-dimensional systems with long-range correlated binary potentials

We study numerically the electronic properties of one-dimensional systems with long-range correlated binary potentials. The potentials are mapped from binary sequences with a power-law power spectrum over the entire frequency range, which is characterized by correlation exponent β. We find the localization length ζ increases withβ. At system sizes N →∞, there are no extended states. However, there exists a transition at a threshold ζ. Whenβ 〉 βc, we obtain ζ 〉 0. On the other hand, at finite system sizes, ζ≥ N may happen at certain β, which makes the system ＂metallic＂, and the upper-bound system size N＊ （β） is given.

Structural, mechanical, electronic properties, and Debye temperature of quaternary carbide Ti3NiAl2C ceramics under high pressure: A first-principles study

Quaternary carbide Ti3NiAl2C ceramics has been investigated as a potential nuclear fusion structural material,and it has advantages in certain aspects compared with Ti2AlC,Ti3AlC2,and Ti3SiC2 structural materials.In this paper,quaternary carbide Ti3NiAl2C ceramics is pressurized to investigate its structural,mechanical,electronic properties,and Debye temperature.Quaternary carbide Ti3NiAl2C ceramics still maintains a cubic structure under pressure(0–110 GPa).At zero pressure,quaternary carbide Ti3NiAl2C ceramics only has three bonds:Ti–Al,Ni–Al,and Ti–C.However,at pressures of 20 GPa,30 GPa,40 GPa,60 GPa,and 70 GPa,new Ti–Ni,Ti–Ti,Al–Al,Ti–Al,and Ti–Ti bonds form.When the pressure reaches 20 GPa,the covalent bonds change to metallic bonds.The volume of quaternary carbide Ti3NiAl2C ceramics can be compressed to 72%of its original volume at most.Pressurization can improve the mechanical strength and ductility of quaternary carbide Ti3NiAl2C ceramics.At 50–60 GPa,its mechanical strength can be comparable to pure tungsten,and the material changes from brittleness to ductility.However,the degree of anisotropy of quaternary carbide Ti3NiAl2C ceramics increases with the increasing pressure.In addition,we also investigated the Debye temperature,density,melting point,hardness,and wear resistance of quaternary carbide Ti3NiAl2C ceramics under pressure.