Polymeric perylene diimide(PDI)has been evidenced as a good candidate for photocatalytic water oxidation,yet the origin of the photocatalytic oxygen evolution activity remains unclear and needs further exploration.Her...Polymeric perylene diimide(PDI)has been evidenced as a good candidate for photocatalytic water oxidation,yet the origin of the photocatalytic oxygen evolution activity remains unclear and needs further exploration.Herein,with crystal and atomic structures of the self-assembled PDI revealed from the X-ray diffraction pattern,the electronic structure is theoretically illustrated by the first-principles density functional theory calculations,suggesting the suitable band structure and the direct electronic transition for efficient photocatalytic oxygen evolution over PDI.It is confirmed that the carbonyl O atoms on the conjugation structure serve as the active sites for oxygen evolution reaction by the crystal orbital Hamiltonian group analysis.The calculations of reaction free energy changes indicate that the oxygen evolution reaction should follow the reaction pathway of H_(2)O→^(*)OH→^(*)O→^(*)OOH→^(*)O_(2)with an overpotential of 0.81 V.Through an in-depth theoretical computational analysis in the atomic and electronic structures,the origin of photocatalytic oxygen evolution activity for PDI is well illustrated,which would help the rational design and modification of polymeric photocatalysts for efficient oxygen evolution.展开更多
The electronic structure,magnetic,and optical properties of two-dimensional(2D)GaSe doped with rare earth elements X(X=Sc,Y,La,Ce,Eu)were calculated using the first-principles plane wave method based on den-sity funct...The electronic structure,magnetic,and optical properties of two-dimensional(2D)GaSe doped with rare earth elements X(X=Sc,Y,La,Ce,Eu)were calculated using the first-principles plane wave method based on den-sity functional theory.The results show that intrinsic 2D GaSe is a p-type nonmagnetic semiconductor with an indi-rect bandgap of 2.6611 eV.The spin-up and spin-down channels of Sc-,Y-,and La-doped 2D GaSe are symmetric,they are non-magnetic semiconductors.The magnetic moments of Ce-and Eu-doped 2D GaSe are 0.908μ_(B)and 7.163μ_(B),which are magnetic semiconductors.Impurity energy levels appear in both spin-up and spin-down chan-nels of Eu-doped 2D GaSe,which enhances the probability of electron transition.Compared with intrinsic 2D GaSe,the static dielectric constant of the doped 2D GaSe increases,and the polarization ability is strengthened.The ab-sorption spectrum of the doped 2D GaSe shifts in the low-energy direction,and the red-shift phenomenon occurs,which extends the absorption spectral range.The optical reflection coefficient of the doped 2D GaSe is improved in the low energy region,and the improvement of Eu-doped 2D GaSe is the most obvious.展开更多
The production of renewable fuels through water splitting via photocatalytic hydrogen production holds significant promise.Nonetheless,the sluggish kinetics of hydrogen evolution and the inadequate water adsorption on...The production of renewable fuels through water splitting via photocatalytic hydrogen production holds significant promise.Nonetheless,the sluggish kinetics of hydrogen evolution and the inadequate water adsorption on photocatalysts present notable challenges.In this study,we have devised a straightforward hydrothermal method to synthesize Bi_(2)O_(3)(BO)derived from metal‐organic frameworks(MOFs),loaded with flower-like ZnIn_(2)S_(4)(ZIS).This approach substantially enhances water adsorption and surface catalytic reactions,resulting in a remarkable enhancement of photocatalytic activity.By employing triethanolamine(TEOA)as a sacrificial agent,the hydrogen evolution rate achieved with 15%(mass fraction)ZIS loading on BO reached an impressive value of 1610μmol∙h^(−1)∙g^(−1),marking a 6.34-fold increase compared to that observed for bare BO.Furthermore,through density functional theory(DFT)and ab initio molecular dynamics(AIMD)calculations,we have identified the reactions occurring at the ZIS/BO S-scheme heterojunction interface,including the identification of active sites for water adsorption and catalytic reactions.This study provides valuable insights into the development of high-performance composite photocatalytic materials with tailored electronic properties and wettability.展开更多
Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe...Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe 3d, while that of hexagonal pyrrhotite is from Fe 3d, Fe 3p and S 3s. The hexagonal pyrrhotite is more reactive than monoclinic pyrrhotite because of large density of states near the Fermi level. The hexagonal pyrrhotite shows antiferromagnetism. S—Fe bonds mainly exist in monoclinic pyrrhotite as the covalent bonds, while hexagonal pyrrhotite has no covalency. The main contributions of higest occupied molecular orbital(HOMO) and lowest unoccupied molecular obital(LUMO) for monoclinic pyrrhotite come from S and Fe. The main contribution of HOMO for hexagonal pyrrhotite comes from Fe, while that of LUMO comes from S. The coefficient of Fe atom is much larger than that of S atom of HOMO for hexagonal pyrrhotite, which contributes to the adsorption of Ca OH+ on the surface of hexagonal pyrrhotite when there is lime. As a result, lime has the inhibitory effect on the floatation of hexagonal pyrrhotite and the coefficient of Fe is very close to that of S for monoclinic pyrrhotite. Therefore, the existence of S prevents the adsorption of Ca OH+on the surface of monoclinic pyrrhotite, which leads to less inhibitory effect on the flotation of monoclinic pyrrhotite.展开更多
The electronic structures of pure V, Nb and Ta metals with bcc structure were determined by one atom (OA) theory. According to the electronic structures of these metals, their potential curves, cohesive energies, latt...The electronic structures of pure V, Nb and Ta metals with bcc structure were determined by one atom (OA) theory. According to the electronic structures of these metals, their potential curves, cohesive energies, lattice parameters, elasticity and the dependence of linear thermal expansion coefficients on temperature were calculated. The electronic structures and characteristic properties of these metals with fcc and hcp structures and liquid states were studied.展开更多
Ab initio calculations are used to understand the fundamental mechanism of the solid solution softening/hardening of the Mo-binary system.The results reveal that the Mo-Ti,Mo-Ta,Mo-Nb,and Mo-W interactions are primari...Ab initio calculations are used to understand the fundamental mechanism of the solid solution softening/hardening of the Mo-binary system.The results reveal that the Mo-Ti,Mo-Ta,Mo-Nb,and Mo-W interactions are primarily attractive with negative heats of formation,while the interactions of Mo-Re,and Mo-Zr would be mainly repulsive with positive heats of formation.It is also shown that the addition of Re and Zr would cause the solid solution softening of Mo by the decrease of the unstable stacking fault energy and the increase of ductility.On the contrary,the elements of W,Ta,Ti,and Nb could bring about the solid-solution hardening of Mo through the impediment of the slip of the dislocation and the decrease of ductility.Electronic structures indicate that the weaker/stronger chemical bonding due to the alloying elements should fundamentally induce the solid solution softening/hardening of Mo.The results are discussed and compared with available evidence in literatures,which could deepen the fundamental understanding of the solid solution softening/hardening of the binary metallic system.展开更多
The electronic structures of pure Ti, Zr and Hf metals with hcp structure were determined by one atom (OA) theory. According to the electronic structures of these metals,their potential curves, cohesive energies, latt...The electronic structures of pure Ti, Zr and Hf metals with hcp structure were determined by one atom (OA) theory. According to the electronic structures of these metals,their potential curves, cohesive energies, lattice constants, elasticities and the temperature dependence of linear thermal expansion coefficients were calculated. The electronic structures and characteristic properties of these metals with bcc and fcc structures and liquids were also studied. The results show that the electronic structures of Ti, Zr and Hf metals are respectively [Ar](3d n) 0.481 0 (3d c) 2.085 7 (4s c) 1.000 0 (4s f) 0.433 3 , [Kr](4d n) 0.396 8 (4d c) 2.142 8 (5s c) 1.262 0 (5s f) 0.198 4 , [Xe](5d n) 0.368 0 (5d c) 2.041 4 (6s c) 1.406 6 (6s f) 0.184 0 . It is explained why the pure Ti, Zr and Hf metals with hcp and bcc structures can exist naturally, while those with fcc structure can not.展开更多
The electronic structure and optical properties of the tetragonal phase quaternary arsenide oxides YZnAsO and LaZnAsO were studied using density-functional theory(DFT) within generalized gradient approximation(GGA).Th...The electronic structure and optical properties of the tetragonal phase quaternary arsenide oxides YZnAsO and LaZnAsO were studied using density-functional theory(DFT) within generalized gradient approximation(GGA).The band structure along the higher symmetry axes in the Brillouin zone,the density of states(DOS) and the partial density of states(PDOS) were presented.The calculated energy band structures show that both YZnAsO and LaZnAsO are indirect gap semiconductors with band gap of 1.173 1 eV and 1.166 5 eV,respectively.The DOS and PDOS show the hybridization of Y-O/La-O atom orbits and Zn-As atom orbits.The dielectric function,reflectivity,absorption coefficient,refractive index,electron energy-loss function and optical conductivity were presented in an energy range from 0 to 25 eV for discussing the optical properties of YZnAsO and LaZnAsO.展开更多
Interfaces play critical roles in electronic devices and provide great diversity of film morphology and device performance.We retrospect the substrate mediated vacuum film growth of benchmark high mobility material 2,...Interfaces play critical roles in electronic devices and provide great diversity of film morphology and device performance.We retrospect the substrate mediated vacuum film growth of benchmark high mobility material 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene(C8-BTBT)and the interface electronic structures.The film growth of C8-BTBT molecules is diversified depending on the substrate-molecule and molecule-molecule interactions.On atomic smooth substrates C8-BTBT film grows in layer-by-layer mode while on coarse substrate it grows in islands mode.The initial molecular layer at dielectric,semiconductor and conductive substrates displays slight different lattice structure.The initial molecule orientation depends on the substrate and will gradually change to standing up configuration as in bulk phase.C8-BTBT behaves as electron donor when contacting with dielectric and stable conductive materials.This usually induces a dipole layer pointing to C8-BTBT and an upward bend bending in C8-BTBT side toward the interface.Although it is air stable,C8-BTBT is chemically reactive with some transition metals and compounds.The orientation change from lying down to standing up in the film usually leads to decrease of ionization potential.The article provides insights to the interface physical and chemical processes and suggestions for optimal design and fabrication of C8-BTBT based devices.展开更多
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(GG...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.展开更多
The electronic structures,chemical bonding,elastic and optical properties of the novel hP24 phase WB3 were investigated by using density-functional theory(DFT) within generalized gradient approximation(GGA).The calcul...The electronic structures,chemical bonding,elastic and optical properties of the novel hP24 phase WB3 were investigated by using density-functional theory(DFT) within generalized gradient approximation(GGA).The calculated energy band structures show that the hP24 phase WB3 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 W 5d and B 2p states.Population analysis suggests that the chemical bonding in hP24-WB3 has predominantly covalent characteristics with mixed covalent-ionic characteristics.Basic physical properties,such as lattice constant,bulk modulus,shear modulus and elastic constants Cij were calculated.The elastic modulus E and Poisson ratio υ were also predicted.The results show that hP24-WB3 phase is mechanically stable and behaves in a brittle manner.Detailed analysis of all optical functions reveals that WB3 is a better dielectric material,and reflectivity spectra show that WB3 can be promised as good coating material in the energy regions of 8.5-11.4 eV and 14.5-15.5 eV.展开更多
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....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.展开更多
The first-principles calculations were performed to investigate the electronic structure, magnetic and dielectric properties of Cr-doped Fe_3C, in comparison to those of pure Fe_3C and Cr_3C. The obtained results show...The first-principles calculations were performed to investigate the electronic structure, magnetic and dielectric properties of Cr-doped Fe_3C, in comparison to those of pure Fe_3C and Cr_3C. The obtained results show that the thermodynamic stability of Crdoped Fe_3C becomes weaker in terms of the larger formation enthalpy, on the contrary, the metallicity and covalency are found to strengthen to some extent. The magnetic moments of Fe_3C, Fe_(11)CrC_4(g), and Fe_(11)CrC_4(s) are respectively 21.36 μB/cell, 16.92 μB/cell, and 17.62 μB/cell, and in Fe_(11)CrC4(g) and Fe_(11)CrC_4(s), the Fe of Wyckoff positions of 8d and 4c is substituted by Cr. The local magnetic moment of Cr at 8d site is larger than that at 4c site in the doped structure, which is opposite to that of Fe. In low frequency band, the permittivity follows the ranking of Fe_(11)Cr C_4(s)>Cr_3C>Fe_(11)Cr C_4(g)>Fe_3C. Once exceeding a certain frequency, the sequence will be broken. Besides the electron transition, the polarization of atoms also makes a contribution to the dielectric properties.展开更多
This paper delves into the theoretical mechanisms of the electronic structure and optical properties of aluminum-based semiconductors(AlX,X=N,P,As,Sb)and indium-based semiconductors(InX,X=N,P,As,Sb)as potential materi...This paper delves into the theoretical mechanisms of the electronic structure and optical properties of aluminum-based semiconductors(AlX,X=N,P,As,Sb)and indium-based semiconductors(InX,X=N,P,As,Sb)as potential materials for optical devices.Band structure calculations reveal that,except for InSb,all other compounds are direct bandgap semiconductors,with AlN exhibiting a bandgap of 3.245 eV.The valence band maximum of these eight compounds primarily stems from the p-orbitals of Al/In and X.In contrast,the conduction band minimum is influenced by all orbitals,with a predominant contribution from the p-orbitals.The static dielectric constant increased with the expansion of the unit cell volume.Compared to AlX and InX with larger X atoms,AlN and InN showed broader absorption spectra in the near-ultraviolet region and higher photoelectric conductance.Regarding mechanical properties,AlN and InN displayed greater shear and bulk modulus than the other compounds.Moreover,among these eight crystal types,a higher modulus was associated with a lower light loss function value,indicating that AlN and InN have superior transmission efficiency and a wider spectral range in optoelectronic material applications.展开更多
The electronic structures of pure Sc and Y metals with hcp structure have been determined by one atom (OA) theory, which are [Ar](3d c) 1.331 5 (4s c) 0.905 0 (4s f) 0.763 5 and [Kr](4d c) 1.293 0 (5s c) 0.947 0 (5s f...The electronic structures of pure Sc and Y metals with hcp structure have been determined by one atom (OA) theory, which are [Ar](3d c) 1.331 5 (4s c) 0.905 0 (4s f) 0.763 5 and [Kr](4d c) 1.293 0 (5s c) 0.947 0 (5s f) 0.760 0 . According to their electronic structure, their potential curves, cohesive energies, lattice constants, elasticity and the temperature dependence of linear thermal expansion coefficients have been calculated. The electronic structures and characteristic properties of these metals with bcc structures and primary liquids have also been studied, which has supplied the structural parameters and property parameters of Sc and Y with different crystal structures and also supplied a series of complete data for the theoretical design of Sc and Y based materials.展开更多
Based on the empirical electronic theory of solids and molecules （EET）, the actual model for unit cell of cementite （0-FeaC） was built and the valence electron structures （VES） of cementite with specified site a...Based on the empirical electronic theory of solids and molecules （EET）, the actual model for unit cell of cementite （0-FeaC） was built and the valence electron structures （VES） of cementite with specified site and a number of Fe atoms substituted by alloying atoms of M （ M=Cr, V, W, Mo, Mn ） were computed by statistical method. By defining P as the stability factor, the stability of alloyed cementite with different numbers and sites of Fe atoms substituted by M was calculated. Calculation results show that the density of lattice electrons, the symmetry of distribution of covalent electron pairs and bond energy have huge influence on the stability of alloyed cementite. It is more stable as M substitutes for FeE than for Fe1. The alloyed cementite is the most stable when Cr, Mo, W and V substitute for 2 atoms of Fe2 at the sites of Nos. 2 and 3 （or No. 6 and No. 7）. The stability of alloyed cementite decreases gradually as being substitutional doped by W, Cr, V, Mo and Mn.展开更多
The equilibrium lattice parameters, electronic structure, bulk modulus, Debye temperature, heat capacity and Gibbs energy of TiB and TiB2 were investigated using the pseudopotential plane-wave method based on density ...The equilibrium lattice parameters, electronic structure, bulk modulus, Debye temperature, heat capacity and Gibbs energy of TiB and TiB2 were investigated using the pseudopotential plane-wave method based on density functional theory (DFT) and the improved quasi-harmonic Debye method. The results show that the total density of states (DOS) of TiB2 is mainly provided by the orbit hybridization of Ti-3d and B-2p states, and the total DOS of TiB is mainly provided by the hybrids bond of Ti-3d and B-2p below the Fermi level and Ti—Ti bond up to the Fermi level. The Ti—B hybrid bond in TiB2 is stronger than that in TiB. Finally, the enthalpy of formation at 0 K, heat capacity and Gibbs free energy of formation at various temperatures were determined. The calculated results are in excellent agreement with the available experimental data.展开更多
Abstract： With the substitution of part Mg in LaMg3 by Cu, the elastic constants CH and C12 increase while C44 decreases, implying an enhanced Poisson effect and smaller resistance to 〈001〉（100） shear. Furthermor...Abstract： With the substitution of part Mg in LaMg3 by Cu, the elastic constants CH and C12 increase while C44 decreases, implying an enhanced Poisson effect and smaller resistance to 〈001〉（100） shear. Furthermore, the bulk modulus B increases, while the shear modulus G, elastic modulus E and anisotropie ratio A are reduced. The calculated Debye temperature of LaCuMg2 is lower, implying the weaker interaction between atoms in LaCuMg2. Then, the stress-strain curves in entire range and the ideal strength at critical strain are studied. The present results show that the lowest ideal tensile strength for LaMg3 and LaCuMg2 is in the 〈100〉 direction. The ideal shear strength on the 〈 1 ^-1 0〉（110） slip system of LaMg3 is greater than LaCuMg2. The density of states and charge density distribution are further studied to understand the inherent mechanism of the mechanical properties.展开更多
NaxCoO2 is a commonly used cathode material for sodium ion batteries because of its easy synthesis, high reversible capacity and good cyclability. The structural and electrochemical properties of NaxCoO2 during sodium...NaxCoO2 is a commonly used cathode material for sodium ion batteries because of its easy synthesis, high reversible capacity and good cyclability. The structural and electrochemical properties of NaxCoO2 during sodium ion insertion/extraction process are studied based on first principles calculations. The calculation results of crystal structure parameters and average intercalation voltage are in good agreement with experiment data. Through calculation of the geometric structure and charge transfer in charging and discharging processes of NaxCoO2, it is found that the oxygen atom surrounding Co of the CoO6 octahedral screens the coulomb potential produced by sodium vacancy in NaxCoO2, and the charge is removed from the entire Co-O layer instead of the Co atom adjacent to sodium vacancy when sodium ions are extracted from the Na CoO2 lattice. Thus, during the insertion/extraction of sodium ion from Na CoO2, the CoO6 octahedral structure undergoes small lattice distortion, which makes the local structure quite stable and is beneficial to the cycling stability of the material for the application of sodium ion batteries.展开更多
Structural stabilities, thermodynamics stabilities, elastic properties and electronic structures of Mgl7Al12, Al2Y and AlaBa phases were analyzed by first-principles calculations with Castep and Drool3 program based o...Structural stabilities, thermodynamics stabilities, elastic properties and electronic structures of Mgl7Al12, Al2Y and AlaBa phases were analyzed by first-principles calculations with Castep and Drool3 program based on the density functional theory. The calculated results of heat of formation indicate that AI2Y phase has the strongest alloying ability. The calculated thermodynamic properties show that the thermal stability of these compounds gradually increases in the order ofMgl7Al12, A12Y and Al4Ba phases. Y or Ba addition to the Mg-Al alloys could improve the heat resistance. The calculated bulk modulus B, shear modulus G, elastic modulus E and Poisson ratio v show that the adding Y or Ba to Mg-Al alloys could promote the brittleness and stiffness, and reduce tenacity and plasticity by forming Al4Ba and Al2Y phases. The calculated cohesive energy and density of state （DOS） show that Al2Y has the strongest structural stability, then AlaBa and finally Mg17Al12. The calculated electronic structures show that Al2Y has the strongest structure stability because of the strong ionic bonds and covalent bonds combined action.展开更多
基金supported by National Natural Science Foundation of China(No.523B2070,No.52225606).
文摘Polymeric perylene diimide(PDI)has been evidenced as a good candidate for photocatalytic water oxidation,yet the origin of the photocatalytic oxygen evolution activity remains unclear and needs further exploration.Herein,with crystal and atomic structures of the self-assembled PDI revealed from the X-ray diffraction pattern,the electronic structure is theoretically illustrated by the first-principles density functional theory calculations,suggesting the suitable band structure and the direct electronic transition for efficient photocatalytic oxygen evolution over PDI.It is confirmed that the carbonyl O atoms on the conjugation structure serve as the active sites for oxygen evolution reaction by the crystal orbital Hamiltonian group analysis.The calculations of reaction free energy changes indicate that the oxygen evolution reaction should follow the reaction pathway of H_(2)O→^(*)OH→^(*)O→^(*)OOH→^(*)O_(2)with an overpotential of 0.81 V.Through an in-depth theoretical computational analysis in the atomic and electronic structures,the origin of photocatalytic oxygen evolution activity for PDI is well illustrated,which would help the rational design and modification of polymeric photocatalysts for efficient oxygen evolution.
文摘The electronic structure,magnetic,and optical properties of two-dimensional(2D)GaSe doped with rare earth elements X(X=Sc,Y,La,Ce,Eu)were calculated using the first-principles plane wave method based on den-sity functional theory.The results show that intrinsic 2D GaSe is a p-type nonmagnetic semiconductor with an indi-rect bandgap of 2.6611 eV.The spin-up and spin-down channels of Sc-,Y-,and La-doped 2D GaSe are symmetric,they are non-magnetic semiconductors.The magnetic moments of Ce-and Eu-doped 2D GaSe are 0.908μ_(B)and 7.163μ_(B),which are magnetic semiconductors.Impurity energy levels appear in both spin-up and spin-down chan-nels of Eu-doped 2D GaSe,which enhances the probability of electron transition.Compared with intrinsic 2D GaSe,the static dielectric constant of the doped 2D GaSe increases,and the polarization ability is strengthened.The ab-sorption spectrum of the doped 2D GaSe shifts in the low-energy direction,and the red-shift phenomenon occurs,which extends the absorption spectral range.The optical reflection coefficient of the doped 2D GaSe is improved in the low energy region,and the improvement of Eu-doped 2D GaSe is the most obvious.
文摘The production of renewable fuels through water splitting via photocatalytic hydrogen production holds significant promise.Nonetheless,the sluggish kinetics of hydrogen evolution and the inadequate water adsorption on photocatalysts present notable challenges.In this study,we have devised a straightforward hydrothermal method to synthesize Bi_(2)O_(3)(BO)derived from metal‐organic frameworks(MOFs),loaded with flower-like ZnIn_(2)S_(4)(ZIS).This approach substantially enhances water adsorption and surface catalytic reactions,resulting in a remarkable enhancement of photocatalytic activity.By employing triethanolamine(TEOA)as a sacrificial agent,the hydrogen evolution rate achieved with 15%(mass fraction)ZIS loading on BO reached an impressive value of 1610μmol∙h^(−1)∙g^(−1),marking a 6.34-fold increase compared to that observed for bare BO.Furthermore,through density functional theory(DFT)and ab initio molecular dynamics(AIMD)calculations,we have identified the reactions occurring at the ZIS/BO S-scheme heterojunction interface,including the identification of active sites for water adsorption and catalytic reactions.This study provides valuable insights into the development of high-performance composite photocatalytic materials with tailored electronic properties and wettability.
基金Project supported by the Open Foundation of Guangxi Key Laboratory for Advanced Materials and Manufacturing Technology,China
文摘Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe 3d, while that of hexagonal pyrrhotite is from Fe 3d, Fe 3p and S 3s. The hexagonal pyrrhotite is more reactive than monoclinic pyrrhotite because of large density of states near the Fermi level. The hexagonal pyrrhotite shows antiferromagnetism. S—Fe bonds mainly exist in monoclinic pyrrhotite as the covalent bonds, while hexagonal pyrrhotite has no covalency. The main contributions of higest occupied molecular orbital(HOMO) and lowest unoccupied molecular obital(LUMO) for monoclinic pyrrhotite come from S and Fe. The main contribution of HOMO for hexagonal pyrrhotite comes from Fe, while that of LUMO comes from S. The coefficient of Fe atom is much larger than that of S atom of HOMO for hexagonal pyrrhotite, which contributes to the adsorption of Ca OH+ on the surface of hexagonal pyrrhotite when there is lime. As a result, lime has the inhibitory effect on the floatation of hexagonal pyrrhotite and the coefficient of Fe is very close to that of S for monoclinic pyrrhotite. Therefore, the existence of S prevents the adsorption of Ca OH+on the surface of monoclinic pyrrhotite, which leads to less inhibitory effect on the flotation of monoclinic pyrrhotite.
文摘The electronic structures of pure V, Nb and Ta metals with bcc structure were determined by one atom (OA) theory. According to the electronic structures of these metals, their potential curves, cohesive energies, lattice parameters, elasticity and the dependence of linear thermal expansion coefficients on temperature were calculated. The electronic structures and characteristic properties of these metals with fcc and hcp structures and liquid states were studied.
基金Project(51801129)supported by the National Natural Science Foundation of ChinaProject supported by the State Key Laboratory of Powder Metallurgy,China。
文摘Ab initio calculations are used to understand the fundamental mechanism of the solid solution softening/hardening of the Mo-binary system.The results reveal that the Mo-Ti,Mo-Ta,Mo-Nb,and Mo-W interactions are primarily attractive with negative heats of formation,while the interactions of Mo-Re,and Mo-Zr would be mainly repulsive with positive heats of formation.It is also shown that the addition of Re and Zr would cause the solid solution softening of Mo by the decrease of the unstable stacking fault energy and the increase of ductility.On the contrary,the elements of W,Ta,Ti,and Nb could bring about the solid-solution hardening of Mo through the impediment of the slip of the dislocation and the decrease of ductility.Electronic structures indicate that the weaker/stronger chemical bonding due to the alloying elements should fundamentally induce the solid solution softening/hardening of Mo.The results are discussed and compared with available evidence in literatures,which could deepen the fundamental understanding of the solid solution softening/hardening of the binary metallic system.
基金TheNaturalScienceFoundationofHunanProvince (No .99JZY10 0 5 )
文摘The electronic structures of pure Ti, Zr and Hf metals with hcp structure were determined by one atom (OA) theory. According to the electronic structures of these metals,their potential curves, cohesive energies, lattice constants, elasticities and the temperature dependence of linear thermal expansion coefficients were calculated. The electronic structures and characteristic properties of these metals with bcc and fcc structures and liquids were also studied. The results show that the electronic structures of Ti, Zr and Hf metals are respectively [Ar](3d n) 0.481 0 (3d c) 2.085 7 (4s c) 1.000 0 (4s f) 0.433 3 , [Kr](4d n) 0.396 8 (4d c) 2.142 8 (5s c) 1.262 0 (5s f) 0.198 4 , [Xe](5d n) 0.368 0 (5d c) 2.041 4 (6s c) 1.406 6 (6s f) 0.184 0 . It is explained why the pure Ti, Zr and Hf metals with hcp and bcc structures can exist naturally, while those with fcc structure can not.
基金Project(50474051) supported by the National Natural Science Foundation of China
文摘The electronic structure and optical properties of the tetragonal phase quaternary arsenide oxides YZnAsO and LaZnAsO were studied using density-functional theory(DFT) within generalized gradient approximation(GGA).The band structure along the higher symmetry axes in the Brillouin zone,the density of states(DOS) and the partial density of states(PDOS) were presented.The calculated energy band structures show that both YZnAsO and LaZnAsO are indirect gap semiconductors with band gap of 1.173 1 eV and 1.166 5 eV,respectively.The DOS and PDOS show the hybridization of Y-O/La-O atom orbits and Zn-As atom orbits.The dielectric function,reflectivity,absorption coefficient,refractive index,electron energy-loss function and optical conductivity were presented in an energy range from 0 to 25 eV for discussing the optical properties of YZnAsO and LaZnAsO.
基金Project(2017YFA0206602)supported in part by the National Key Research and Development Program of China。
文摘Interfaces play critical roles in electronic devices and provide great diversity of film morphology and device performance.We retrospect the substrate mediated vacuum film growth of benchmark high mobility material 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene(C8-BTBT)and the interface electronic structures.The film growth of C8-BTBT molecules is diversified depending on the substrate-molecule and molecule-molecule interactions.On atomic smooth substrates C8-BTBT film grows in layer-by-layer mode while on coarse substrate it grows in islands mode.The initial molecular layer at dielectric,semiconductor and conductive substrates displays slight different lattice structure.The initial molecule orientation depends on the substrate and will gradually change to standing up configuration as in bulk phase.C8-BTBT behaves as electron donor when contacting with dielectric and stable conductive materials.This usually induces a dipole layer pointing to C8-BTBT and an upward bend bending in C8-BTBT side toward the interface.Although it is air stable,C8-BTBT is chemically reactive with some transition metals and compounds.The orientation change from lying down to standing up in the film usually leads to decrease of ionization potential.The article provides insights to the interface physical and chemical processes and suggestions for optimal design and fabrication of C8-BTBT based devices.
基金Project(20080431025) supported by Chinese Postdoctoral Science FoundationProject(08JJ3005) supported by Hunan Provincial Natural Science Foundation of ChinaProject(2007) supported by Postdoctoral Science Foundation of Central South University,China
文摘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.
基金Project(11271121)supported by the National Natural Science Foundation of ChinaProject(11JJ2002)supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(11K038)supported by Key Laboratory of Computational and Stochastic Mathematics of Ministry of Education of ChinaProject(2013GK3130)supported by the Scientific and Technological Plan of Hunan Province,China
文摘The electronic structures,chemical bonding,elastic and optical properties of the novel hP24 phase WB3 were investigated by using density-functional theory(DFT) within generalized gradient approximation(GGA).The calculated energy band structures show that the hP24 phase WB3 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 W 5d and B 2p states.Population analysis suggests that the chemical bonding in hP24-WB3 has predominantly covalent characteristics with mixed covalent-ionic characteristics.Basic physical properties,such as lattice constant,bulk modulus,shear modulus and elastic constants Cij were calculated.The elastic modulus E and Poisson ratio υ were also predicted.The results show that hP24-WB3 phase is mechanically stable and behaves in a brittle manner.Detailed analysis of all optical functions reveals that WB3 is a better dielectric material,and reflectivity spectra show that WB3 can be promised as good coating material in the energy regions of 8.5-11.4 eV and 14.5-15.5 eV.
基金Project(2014GXNSFAA118342)supported by Guangxi Natural Science Foundation,ChinaProject supported by Open Foundation of Guangxi Key Laboratory for Advanced Materials and Manufacturing Technology,ChinaProject supported by High-level Innovation Team and Outstanding Scholar Program in Guangxi Colleges(the second batch),China
文摘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.
基金Project(51174252)supported by the Joint Funds of the National Natural Science Foundation of China
文摘The first-principles calculations were performed to investigate the electronic structure, magnetic and dielectric properties of Cr-doped Fe_3C, in comparison to those of pure Fe_3C and Cr_3C. The obtained results show that the thermodynamic stability of Crdoped Fe_3C becomes weaker in terms of the larger formation enthalpy, on the contrary, the metallicity and covalency are found to strengthen to some extent. The magnetic moments of Fe_3C, Fe_(11)CrC_4(g), and Fe_(11)CrC_4(s) are respectively 21.36 μB/cell, 16.92 μB/cell, and 17.62 μB/cell, and in Fe_(11)CrC4(g) and Fe_(11)CrC_4(s), the Fe of Wyckoff positions of 8d and 4c is substituted by Cr. The local magnetic moment of Cr at 8d site is larger than that at 4c site in the doped structure, which is opposite to that of Fe. In low frequency band, the permittivity follows the ranking of Fe_(11)Cr C_4(s)>Cr_3C>Fe_(11)Cr C_4(g)>Fe_3C. Once exceeding a certain frequency, the sequence will be broken. Besides the electron transition, the polarization of atoms also makes a contribution to the dielectric properties.
文摘This paper delves into the theoretical mechanisms of the electronic structure and optical properties of aluminum-based semiconductors(AlX,X=N,P,As,Sb)and indium-based semiconductors(InX,X=N,P,As,Sb)as potential materials for optical devices.Band structure calculations reveal that,except for InSb,all other compounds are direct bandgap semiconductors,with AlN exhibiting a bandgap of 3.245 eV.The valence band maximum of these eight compounds primarily stems from the p-orbitals of Al/In and X.In contrast,the conduction band minimum is influenced by all orbitals,with a predominant contribution from the p-orbitals.The static dielectric constant increased with the expansion of the unit cell volume.Compared to AlX and InX with larger X atoms,AlN and InN showed broader absorption spectra in the near-ultraviolet region and higher photoelectric conductance.Regarding mechanical properties,AlN and InN displayed greater shear and bulk modulus than the other compounds.Moreover,among these eight crystal types,a higher modulus was associated with a lower light loss function value,indicating that AlN and InN have superior transmission efficiency and a wider spectral range in optoelectronic material applications.
文摘The electronic structures of pure Sc and Y metals with hcp structure have been determined by one atom (OA) theory, which are [Ar](3d c) 1.331 5 (4s c) 0.905 0 (4s f) 0.763 5 and [Kr](4d c) 1.293 0 (5s c) 0.947 0 (5s f) 0.760 0 . According to their electronic structure, their potential curves, cohesive energies, lattice constants, elasticity and the temperature dependence of linear thermal expansion coefficients have been calculated. The electronic structures and characteristic properties of these metals with bcc structures and primary liquids have also been studied, which has supplied the structural parameters and property parameters of Sc and Y with different crystal structures and also supplied a series of complete data for the theoretical design of Sc and Y based materials.
基金Project(2014CFB801)supported by Natural Science Foundation of Hubei Province of ChinaProject(11304236)supported by the National Natural Science Foundation of China
文摘Based on the empirical electronic theory of solids and molecules （EET）, the actual model for unit cell of cementite （0-FeaC） was built and the valence electron structures （VES） of cementite with specified site and a number of Fe atoms substituted by alloying atoms of M （ M=Cr, V, W, Mo, Mn ） were computed by statistical method. By defining P as the stability factor, the stability of alloyed cementite with different numbers and sites of Fe atoms substituted by M was calculated. Calculation results show that the density of lattice electrons, the symmetry of distribution of covalent electron pairs and bond energy have huge influence on the stability of alloyed cementite. It is more stable as M substitutes for FeE than for Fe1. The alloyed cementite is the most stable when Cr, Mo, W and V substitute for 2 atoms of Fe2 at the sites of Nos. 2 and 3 （or No. 6 and No. 7）. The stability of alloyed cementite decreases gradually as being substitutional doped by W, Cr, V, Mo and Mn.
基金Project(07JJ3102)supported by the Natural Science Foundation of Hunan Province,ChinaProject(k0902132-11)supported by the Changsha Municipal Science and Technology,China
文摘The equilibrium lattice parameters, electronic structure, bulk modulus, Debye temperature, heat capacity and Gibbs energy of TiB and TiB2 were investigated using the pseudopotential plane-wave method based on density functional theory (DFT) and the improved quasi-harmonic Debye method. The results show that the total density of states (DOS) of TiB2 is mainly provided by the orbit hybridization of Ti-3d and B-2p states, and the total DOS of TiB is mainly provided by the hybrids bond of Ti-3d and B-2p below the Fermi level and Ti—Ti bond up to the Fermi level. The Ti—B hybrid bond in TiB2 is stronger than that in TiB. Finally, the enthalpy of formation at 0 K, heat capacity and Gibbs free energy of formation at various temperatures were determined. The calculated results are in excellent agreement with the available experimental data.
基金Project(51071053)supported by the National Natural Science Foundation of ChinaProject(X071117)supported by the Scientific Research Foundation of Guangxi University,ChinaProject(KF0803)supported by the Open Project of Key Laboratory of Materials Design and Preparation Technology of Hunan Province,China
文摘Abstract： With the substitution of part Mg in LaMg3 by Cu, the elastic constants CH and C12 increase while C44 decreases, implying an enhanced Poisson effect and smaller resistance to 〈001〉（100） shear. Furthermore, the bulk modulus B increases, while the shear modulus G, elastic modulus E and anisotropie ratio A are reduced. The calculated Debye temperature of LaCuMg2 is lower, implying the weaker interaction between atoms in LaCuMg2. Then, the stress-strain curves in entire range and the ideal strength at critical strain are studied. The present results show that the lowest ideal tensile strength for LaMg3 and LaCuMg2 is in the 〈100〉 direction. The ideal shear strength on the 〈 1 ^-1 0〉（110） slip system of LaMg3 is greater than LaCuMg2. The density of states and charge density distribution are further studied to understand the inherent mechanism of the mechanical properties.
基金Project(51472211)supported by the National Natural Science Foundation of ChinaProject(2012CK1006)supported by Scientific and Technical Achievement Transformation Fund of Hunan Province,China
文摘NaxCoO2 is a commonly used cathode material for sodium ion batteries because of its easy synthesis, high reversible capacity and good cyclability. The structural and electrochemical properties of NaxCoO2 during sodium ion insertion/extraction process are studied based on first principles calculations. The calculation results of crystal structure parameters and average intercalation voltage are in good agreement with experiment data. Through calculation of the geometric structure and charge transfer in charging and discharging processes of NaxCoO2, it is found that the oxygen atom surrounding Co of the CoO6 octahedral screens the coulomb potential produced by sodium vacancy in NaxCoO2, and the charge is removed from the entire Co-O layer instead of the Co atom adjacent to sodium vacancy when sodium ions are extracted from the Na CoO2 lattice. Thus, during the insertion/extraction of sodium ion from Na CoO2, the CoO6 octahedral structure undergoes small lattice distortion, which makes the local structure quite stable and is beneficial to the cycling stability of the material for the application of sodium ion batteries.
基金Project(2011DFA50520) supported by the International Cooperation of Ministry of Science and Technology of ChinaProject(50975263) supported by the National Natural Science Foundation of ChinaProject(2010-78) supported by the Shanxi Provincial Foundation for Returned Scholars,China
文摘Structural stabilities, thermodynamics stabilities, elastic properties and electronic structures of Mgl7Al12, Al2Y and AlaBa phases were analyzed by first-principles calculations with Castep and Drool3 program based on the density functional theory. The calculated results of heat of formation indicate that AI2Y phase has the strongest alloying ability. The calculated thermodynamic properties show that the thermal stability of these compounds gradually increases in the order ofMgl7Al12, A12Y and Al4Ba phases. Y or Ba addition to the Mg-Al alloys could improve the heat resistance. The calculated bulk modulus B, shear modulus G, elastic modulus E and Poisson ratio v show that the adding Y or Ba to Mg-Al alloys could promote the brittleness and stiffness, and reduce tenacity and plasticity by forming Al4Ba and Al2Y phases. The calculated cohesive energy and density of state （DOS） show that Al2Y has the strongest structural stability, then AlaBa and finally Mg17Al12. The calculated electronic structures show that Al2Y has the strongest structure stability because of the strong ionic bonds and covalent bonds combined action.
