Fine-tuning electronic structure of N-doped graphitic carbon-supported Co-and Fe-incorporated Mo_(2)C to achieve ultrahigh electrochemical water oxidation activity

Mo_(2)C is an excellent electrocatalyst for hydrogen evolution reaction(HER).However,Mo_(2)C is a poor electrocatalyst for oxygen evolution reaction(OER).Herein,two different elements,namely Co and Fe,are incorporated in Mo_(2)C that,therefore,has a finely tuned electronic structure,which is not achievable by incorporation of any one of the metals.Consequently,the resulting electrocatalyst Co_(0.8)Fe_(0.2)-Mo_(2)C-80 displayed excellent OER catalytic performance,which is evidenced by a low overpotential of 214.0(and 246.5)mV to attain a current density of 10(and 50)mA cm^(-2),an ultralow Tafel slope of 38.4 mV dec^(-1),and longterm stability in alkaline medium.Theoretical data demonstrates that Co_(0.8)Fe_(0.2)-Mo_(2)C-80 requires the lowest overpotential(1.00 V)for OER and Co centers to be the active sites.The ultrahigh catalytic performance of the electrocatalyst is attributed to the excellent intrinsic catalytic activity due to high Brunauer-Emmett-Teller specific surface area,large electrochemically active surface area,small Tafel slope,and low chargetransfer resistance.

Mechanical properties and electronic structures of MgCu_2, Mg_2Ca and MgZn_2 Laves phases by first principles calculations

Mechanical properties and electronic structure of MgCu2, Mg2 Ca and MgZn2 phases were investigated by means of first principles calculations from CASTEP program based on density functional theory（DFT）. The calculated lattice parameters are in good agreement with the experimental and literature values. The calculated heat of formation and cohesive energies showed that MgCu2 has the strongest alloying ability and structural stability. Elastic constants of MgCu2, Mg2 Ca and MgZn2 were calculated, and the bulk moduli, shear moduli, elastic moduli and Poisson ratio were derived. The calculated results show that MgCu2, Mg2 Ca and MgZn2 are all ductile phases. Among the three phases, MgCu2 has the strongest stiffness and the plasticity of MgZn2 phase is the best. Melting points of the three phases were predicted using cohesive energy and elastic constants. Density of states（DOS）, Mulliken population, electron occupation number and charge density difference were discussed. Finally, Debye temperature was calculated and discussed.

Correlation between electronic structure and energy band in Eu-doped CuInTe_2 semiconductor compound with chalcopyrite structure

The Eu-doped Cu（In, Eu）Te2 semiconductors with chalcopyrite structures are promising materials for their applications in the absorption layer for thin-film solar cells due to their wider band-gaps and better optical properties than those of CuInTe2. In this paper, the Eu-doped CuInTe2 （CuIn1-xEuxTe2, x = 0, 0.1, 0.2, 0.3） are studied systemically based on the empirical electron theory （EET）. The studies cover crystal structures, bonding regularities, cohesive energies, energy levels, and valence electron structures. The theoretical values fit the experimental results very well. The physical mechanism of a broadened band-gap induced by Eu doping into CuInTe2 is the transitions between different hybridization energy levels induced by electron hopping between s and d orbitals and the transformations from the lattice electrons to valence electrons for Cu and In ions. The research results reveal that the photovoltaic effect induces the increase of lattice electrons of In and causes the electric resistivity to decrease. The Eu doping into CuInTe2 mainly influences the transition between different hybridization energy levels for Cu atoms, which shows that the 3d electron numbers of Cu atoms change before and after Eu doping. In single phase CuIn1-xEuxTe2, the number of valence electrons changes regularly with increasing Eu content, and the calculated band gap Eg also increases, which implies that the optical properties of Eu-doped CuIn1-xEuxTe2 are improved.

First principles calculation of electronic structure, chemical bonding and elastic properties of ultra-incompressible Re_2P

The electronic structures, chemical bonding and elastic properties of the Co2P-type structure phase ultra-incompressible Re2P （orthorhombic phase） were investigated by density-functional theory （DFT） within generalized gradient approximation （GGA）. The calculated energy band structures show that the orthorhombic structure phase Re2P is metallic material. The density of state （DOS） and the partial density of state （PDOS） calculations show that the DOS near the Fermi level is mainly from the Re-5d state. Population analysis suggests that the chemical bonding in Re2P has predominantly covalent character with mixed covalent-ionic character. Basic physical properties, such as lattice constant, bulk modulus, shear modulus, and elastic constants Cij, were calculated. The elastic modulus and Poisson ratio were also predicted. The results show that the Co2P-type structure phase Re2P is mechanically stable and behaves in a brittle manner.

Synthesis and Electronic Structure of A2B Type Halogen Atoms Substituted H3-Triarylcorroles

Seven electron-deficient A_2 B type H_3-triarylcorroles have been synthesized and characterized. The solvent dependence of the electronic absorption and magnetic circular dichroism（MCD） spectra and a series of TD-DFT calculations have been used to analyze trends in the electronic structures. Significant differences are observed in the optical spectra when solvents of differing polarity are used,which can be assigned to the effect of NH-tautomerism.

Experimental Investigation of Electronic Structure of La(O,F)BiSe_2

La（O,F）BiSe2 is a layered superconductor and has the same crystal structure with La（O,F）BiS2. We investigate the electronic structure of La（O,F）BiSe2 using the angle-resolved photoemission spectroscopy. Two electron-like Fermi surfaces around X（π, 0） are observed, corresponding to the electron doping of 0.23 per Bi site. We clearly resolve anisotropic band splitting along both Г-X and M-X due to the cooperative effects of large spin-orbit coupling and interlayer coupling. Moreover, we observe an almost non-dispersive electronic state around -0.2 eV between the electron-like bands. This state vanishes after in-situ K evaporation, indicating that it could be the localized surface state caused by defects on the cleaved surface.

Boosting oxygen evolution reactivity by modulating electronic structure and honeycomb-like architecture in Ni_(2)P/N,P-codoped carbon hybrids

Oxygen evolution reaction(OER)as the foremost stumbling block to generate cost-effective clean fuels has received extensive attention in recent years.But,it still maintains the challenge to manipulate the geometric and electronic structure during single reaction process under the same conditions.Herein,we report a simple self-template strategy to generate honeycomb-like Ni_(2)P/N,P-C hybrids with preferred electronic architecture.Experiments coupled with theoretical results revealed that the synthesized catalyst has two characteristics:firstly,the unique honeycomb-like morphology not only enables the fully utilization of catalytic active sites but also optimizes the mass/electron transportation pathway,which favor the diffusion of electrolyte to accessible active sites.Secondly,N,P-C substrate,on the one hand,largely contributes the electronic distribution near Fermi level(E_(F))thus boosting its electrical conductivity.On the other hand,the support effect result in the upshift of d-band center and electropositivity of Ni sites,which attenuates the energy barrier for the adsorption of OH~àand the formation of*OOH.In consequence,the optimized Ni_(2)P/N,P-C catalysts feature high electrocatalytic activity towards OER(a low overpotential of 252 m V to achieve10 m A cm^(-2))and 10 h long-term stability,the outstanding performance is comparable to most of transition metal catalysts.This work gives a innovative tactics for contriving original OER electrocatalysts,inspirng deeper understanding of fabricating catalysts by combining theoretical simulation and experiment design.

LOCALIZED STUDIES ON ELECTRONIC STRUCTURE AND CHEMICAL BOND FOR [NCCuS_2MoS_2]^(2-) CLUSTER

The canonical and locatized molecutar orbiters of [NCCuS_2NoS_2]^(2-) cluster were calculated by means of CNDO quantum chemistry method. Then the energy and properties of corresponding chemicat bonds were discussed, especially, Cu-Sb-No three center conjugated π bonds and No-St-No conjugated π bonds were accounted for.

Tuning the Electronic Structure of Sr2IrO4 Thin Films by Bulk Electronic Doping Using Molecular Beam Epitaxy

By means of oxide molecular beam epitaxy with shutter-growth mode, we fabricate a series of electron-doped （Sr1-xLax）2IrO4 （001） （x=0, 0.05, 0.1 and 0.15） single crystalline thin films and then investigate the doping dependence of the electronic structure utilizing in-situ angle-resolved photoemission spectroscopy. It is found that with the increasing doping content, the Fermi levels of samples progressively shift upward. Prominently, an extra electron pocket crossing the Fermi level around the M point is evidently observed in the 15% nominal doping sample. Moreover, bulk-sensitive transport measurements confirm that the doping effectively suppresses the insulating state with respect to the as-grown Sr2IrO4, though the doped samples still remain insulating at low temperatures due to the localization effect possibly stemming from disorders including oxygen deficiencies. Our work provides another feasible doping method to tune electronic structure of Sr2 IrO4.

INDO STUDIES ON THE ELECTRONIC STRUCTURE OF[Ln(CCl_3COO)_3·phen·C_2H_5OH]_2(Ln=Pr,Sm)

The electronic structure and chemical bonding of the title comp- lexes have been studied by an unrestricted INDO program made applicable for the lanthanoid compounds.The results indicated:(1)In coordinated bonds O-Ln and N-Ln,5d orbitals of Ln have large contribution in all valence orbitals of Ln and 4f orbitals have very small contribution.(2)The covalent chara- cter and ionic character are almost equal in the chemical bond which is comparatively weak between phen,C_2H_5OH and Ln are mainly ionic with some covalent character.

First-principles Study on the Electronic Structure of Novel Titanium Yttrium Mixed-metal Nitride Clusterfullerene

We present a first-principles study on the geometric, vibrational and electronic properties of a novel Y-based non-scandium mixed-metal nitride clusterfullerene （TiY2N@C80）. Theoretical results indicate that the fundamental electronic properties of TiY2N@C80 are similar to that of TiSc2N@C80, but dramatically different from that of ScaN@C800 and YaN@C80 molecules. We find that the magnetism of TiY2N@C80 is quenched by carrier doping. The rotation energy barrier of the TiY2N cluster in C80 cage was obviously increased by exohedral chemical modification with pyrrolidine monoadduct.

Influences of Li Intercalation on the Electronic Structures of O2p and V3d Orbitals in α-V205

The influence of Li intercalation on the electronic structures of oxygen and vanadium ions in α-V205 was investigated using first-principles calculations based on the density functional theory with local density approximation. Two different intercalation sites for Li in the V205 lattices were considered. The calculation results demonstrate that intercalated Li ions at different sites show different effects on the electronic structures of O2p and V3d orbitals. But in both cases Li intercalation will weaken the V---O1 bonding and cause the split-off in V3d valence band to narrow or even disappear and simultaneously broaden the O2p conduction band. Further, the average electron transfer number from per intercalated Li2s to V3d orbitals is determined to total be about 0.52.

First-Principles Investigation of Energetics and Electronic Structures of Ni and Sc Co-Doped MgH2

First-principles calculations were used to study the energetics and electronic structures of Ni and Sc co-doped MgH2 system. The preferential positions for dopants were determined by the minimal total electronic energy. The results of formation enthalpy indicate that Ni and Sc co-doped MgH2 system is more stable than Ni single-doped system. The hydrogen desorption enthalpies of these two hydrides are investigated. Ni and Sc co-doping can improve the dehydrogenation properties of MgH2. The lowest hydrogen desorption enthalpy of 0.30 eV appears in co-doped system, which is significantly lower than that of Ni doping. The electronic structure analysis illustrates that the hybridization of dopants with Mg and H atom together weakens the Mg-H interaction. And the Mg-H bonds are more susceptible to dissociate by Ni and Sc co-doping because of the reduced magnitude of Mg-H hybridization peaks. These behaviors effectively improve the dehydrogenation properties of Ni and Sc co-doped cases.

Effects of N-doping concentration on the electronic structure and optical properties of N-doped β-Ga_2O_3

The electronic structures and the optical properties of N-doped β-Ga2O3 with different N-doping concentrations are studied using the first-principles method.We find that the N substituting O（1） atom is the most stable structure for the smallest formation energy.After N-doping,the charge density distribution significantly changes,and the acceptor impurity level is introduced above the valence band and intersects with the Fermi level.The impurity absorption edges appear to shift toward longer wavelengths with an increase in N-doping concentration.The complex refractive index shows metallic characteristics in the N-doped β-Ga2O3.

The First Principle Calculation of Electronic Structure and Optical Properties of CdGeAs_2

The electronic structure and optical properties of CdGeAs2 were calculated by the first principle method using ultra-soft pseudo-potential approach of the plane wave based upon density functional theory （DFT）. Mulliken population analysis showed that atomic orbital hybridization occurs when forming chemical bonds. The relationship between inter-band transition and optical properties was analyzed to provide a theoretical basis for investigating or controlling CdGeAs2 crystal defects.

Studies on the Electronic Structures of the C_60, C_60H_60 and C_60F_60

The present paper represents the electronic structures of the cluster C60 and its derivatives C60H60 and C60F60 with FOOT-type of structure. On the basis of the total energies and molecular orbital energies from CNDO/2 calculations the clusters' stabilities, electronic configurations and charge distributions are discussed. The calculation results and discussion are very beneficial to understanding physical and chemical properties of the cluster C60 and its derivatives.

First-principle investigation on electronic structures and elastic properties of Al-doped MoSi_2

The electronic structures and elastic properties of Al-doped MoSi2 were calculated using the plane wave pseudo-potential method based on the density functional theory,in which the generalized-gradient approximation(GGA) was used to describe the exchange-correlation potential.Starting from the elastic constants,bulk modulus,shear modulus,elastic modulus and Poisson ratio of Al-doped MoSi2 were obtained by using the Hill method.The results indicate that conductivity of Al-doped MoSi2 is improved to some extent in comparison with that of pure MoSi2 due to the orbit hybridization of Mo 4d,Al 3p and Si 3p electrons.In addition,calculations show that the elastic modulus and the brittleness of Al-doped MoSi2 are smaller than those of pure MoSi2,which implies that it is feasible to toughen MoSi2 by doping Al.The agreement of the conclusion with experiment shows that the present theory is reasonable.

First-principle study of electronic structure and optical properties of Au-doped VO2

The electronic structure and optical properties of VO2 and Au-VO2 were studied using density functional theory. The calculation results show that the interaction between Au and O is stronger than that between V and O. There exists not only the covalent bonding but also ionic bonding in Au--O bond. The band gap of Au-VO2 is smaller than that of VO〉 while the dielectric constant, conductivity, and intensity of optical absorption of Au-VO2 are larger than those of VO2.

First-principles Study on the Electronic Structure and Stability of Mo_(2-x)Cr_xC

This paper deals with the electronic structure and stability of a series of carbides Mo2-xCrxC based on the pseudopotential plane-waves approach of density functional theory and using the generalized gradient approximation(GGA) for the exchange and correlation potential.The calculation results of formation energies demonstrate that the structure Mo2-xCrxC in range of 0≤x≤1.75 is stable under ambient conditions.The formation energies/stabilities of the structures Mo2-xCrxC increase /reduce with enhancing the content of Cr in the structure.Calculated density of state(DOS) show that an increase in the content of Cr dissolving in Mo2-xCrxC crystal cell can lead to the crystal cell volume slightly to shrinkage,TDOS to be elevated at the Fermi level and the peak value of DOS to decrease at the lower energy region from-13.78 to-10.16 eV.Mulliken population analysis explains that the Mo2-xCrxC phase possess the metallic,covalent and ionic bonds.

Evolution of incommensurate superstructure and electronic structure with Pb substitution in(Bi2-xPbx)Sr2CaCu2O8+δ superconductors

High-quality Bi2-xPbxSr2 CaCu2O8+δ(Bi2212) single crystals have been successfully grown by the traveling solvent floating zone technique with a wide range of Pb substitution(x = 0–0.8).The samples are characterized by transmission electron microscope(TEM) and measured by high resolution laser-based angle-resolved photoemission spectroscopy(ARPES) with different photon energies.A systematic evolution of the electronic structure and superstructure with Pb substitution has been revealed for the first time.The superstructure shows a significant change with Pb substitution and the incommensurate modulation vector(Q) decreases with increasing Pb substitution.In the meantime, the superstructure intensity from ARPES measurements also decreases dramatically with increasing Pb concentration.The superstructure in Bi2212 can be effectively suppressed by Pb substitution and it nearly disappears with a Pb substitution of x = 0.8.We also find that the superstructure bands in ARPES measurements depend sensitively on the photon energy of lasers used;they can become even stronger than the main band when using a laser photon energy of 10.897 eV.These results provide important information on the origin of the incommensurate superstructure and its control and suppression in bismuth-based high temperature superconductors.