The electronic properties and stability of Li-doped ZnO with various defects have been stud- ied by calculating the electronic structures and defect formation energies via first-principles calculations using hybrid Ha...The electronic properties and stability of Li-doped ZnO with various defects have been stud- ied by calculating the electronic structures and defect formation energies via first-principles calculations using hybrid Hartree-Fock and density functional methods. The results from formation energy calculations show that Li pair complexes have the lowest formation energy in most circumstances and they consume most of the Li content in Li doped ZnO, which make the p-type conductance hard to obtain. The formation of Li pair complexes is the main obstacle to realize p-type conductance in Li doped ZnO. However, the formation energy of Lizn decreases as environment changes from Zn-rich to O-rich and becomes more stable than that of Li-pair complexes at highly O-rich environment. Therefore, p-type conductance can be obtained by Li doped ZnO grown or post annealed in oxygen rich atmosphere.展开更多
It has been demonstrated that intermolecular interaction,crucial in a plenty of chemical and physical processes,may vary in the presence of metal surface.However,such modification is yet to be quantitatively revealed....It has been demonstrated that intermolecular interaction,crucial in a plenty of chemical and physical processes,may vary in the presence of metal surface.However,such modification is yet to be quantitatively revealed.Here,we present a systematical density functional theory study on adsorbed bis（para-pyridyl）acetylene（BPPA） tetramer on Au（111） surface.We observed unusually high electron density between two head-to-head N atoms,an intermolecular ＂non-bonded＂ region,in adsorbed BPPA tetramer.This exceptional electron density originates from the wavefunction hybridization of the two compressed N lone-electron-pair states of two BPPA,as squeezed by a newly revealed N-Au-N threecenter bonding.This bond,together with the minor contribution from N...H-C intermolecular hydrogen bonding,shortens the N-N distance from over 4 A to 3.30 A and offers an attractive lateral interacting energy of 0.60 eV,effectively to a surface-confined in-plane pressure.The overlapped non-bonding vvavefunction hybridization arising from the effective pressure induced by the N-Au-N three-center bonding,as not been fully recognized in earlier studies,was manifested in non-contact Atomic Force Microscopy.展开更多
A theoretical study on the reaction of aluminum with water in the gas phase was performed using the hybrid density functional B3LYP and QCISD（T） methods with the 6-311＋G（d,p） and the 6-311＋＋G（d,p） basis sets....A theoretical study on the reaction of aluminum with water in the gas phase was performed using the hybrid density functional B3LYP and QCISD（T） methods with the 6-311＋G（d,p） and the 6-311＋＋G（d,p） basis sets. The results show that there are three possible reaction pathways that involve four isomers, seven transition structures, and two possible products for the reaction of aluminum with water. The two most favorable reaction pathways were found, whose intermediates and products agreed quite well with experimental results. The enthalpy and Gibbs free energy change of the reaction between A1 and H2O at 298 and 2000 K were calculated. Some results are also in good agreement with the previous calculations or experimental results.展开更多
The crystal structure, band structure, density of states, Mulliken charge, bond population and optical properties for LiBi_（1-x）M_xO_3（M=V, Nb, and Ta） were investigated using hybrid density functional theory. It ...The crystal structure, band structure, density of states, Mulliken charge, bond population and optical properties for LiBi_（1-x）M_xO_3（M=V, Nb, and Ta） were investigated using hybrid density functional theory. It was found that LiBiO_3 doped with V, Nb, and Ta presented distinctly stronger covalent interactions in M-O（M=V, Nb, and Ta） than Bi-O, thus resulting in mild distortion of the structure and facilitating the separation of photogenerated carriers. Furthermore, the hybridizations of Bi-6s, M-d（M=V, Nb, and Ta） and O-2p widened the valence and conduction bands, which promoted transmission of photogenerated carriers in the band edge and thus caused better photocatalytic performance.展开更多
Using first-principles calculations, we investigate the two-dimensional arsenic nanosheet isolated from bulk gray arsenic. Its dynamical stability is confirmed by phonon calculations and molecular dynamics analyzing. ...Using first-principles calculations, we investigate the two-dimensional arsenic nanosheet isolated from bulk gray arsenic. Its dynamical stability is confirmed by phonon calculations and molecular dynamics analyzing. The arsenic sheet is an indirect band gap semiconductor with a band gap of 2.21 e V in the hybrid HSE06 functional calculations. The valence band maximum（VBM） and the conduction band minimum（CBM） are mainly occupied by the 4p orbitals of arsenic atoms,which is consistent with the partial charge densities of VBM and CBM. The charge density of the VBM G point has the character of a π bond, which originates from p orbitals. Furthermore, tensile and compressive strains are applied in the armchair and zigzag directions, related to the tensile deformations of zigzag and armchair nanotubes, respectively. We find that the ultimate strain in zigzag deformation is 0.13, smaller than 0.18 of armchair deformation. The limit compressive stresses of single-layer arsenic along armchair and zigzag directions are-4.83 GPa and-4.76 GPa with corresponding strains of-0.15 and-0.14, respectively.展开更多
The formation, structural and electronic properties of silicene oxides（SOs） that result from the oxidation of silicene on Ag（111） surface have been investigated in the framework of density functional theory（DFT）...The formation, structural and electronic properties of silicene oxides（SOs） that result from the oxidation of silicene on Ag（111） surface have been investigated in the framework of density functional theory（DFT）.It is found that the honeycomb lattice of silicene on the Ag（111） surface changes after the oxidation. SOs are strongly hybridized with the Ag（111） surface so that they possess metallic band structures. Charge accumulation between SOs and the Ag（111） surface indicates strong chemical bonding, which dramatically affects the electronic properties of SOs. When SOs are peeled off the Ag（111） surface, however, they may become semiconductors.展开更多
Hybrid density functional calculations was used to comprehensively study the electronic structure of S-,Snand Pb-monodoped and（Sn,S）-and（Pb,S）-codoped hexagonal WO_3（h-WO_3）in order to improve their visible ligh...Hybrid density functional calculations was used to comprehensively study the electronic structure of S-,Snand Pb-monodoped and（Sn,S）-and（Pb,S）-codoped hexagonal WO_3（h-WO_3）in order to improve their visible light photocatalytic activity.Results indicate that the（Sn,S）-and（Pb,S）-codoped h-WO_3 can realize a significant band gap reduction and prevent the formation of empty states in the valence band of h-WO_3,while Sn/Pb-monodoped h-WO_3 cannot,because in（Sn,S）-and（Pb,S）-codoping,the S-doping introduces the fully occupied S 3p states in the forbidden band gap of h-WO_3 and the acceptor metals（Sn and Pb）would assist the coupling of the introduced S with its nearest O.In particular,the（Sn,S）-codoped h-WO_3 has the narrowest band gap of 1.85 eV and highest reducing ability among the doped case.Moreover,the calculated optical absorption spectra show that（Sn,S）-codoping can improve the visible light absorption.In short,these results indicate that the（Sn,S）-codoped h-WO_3 is a promising material in solar-driven water splitting.展开更多
文摘The electronic properties and stability of Li-doped ZnO with various defects have been stud- ied by calculating the electronic structures and defect formation energies via first-principles calculations using hybrid Hartree-Fock and density functional methods. The results from formation energy calculations show that Li pair complexes have the lowest formation energy in most circumstances and they consume most of the Li content in Li doped ZnO, which make the p-type conductance hard to obtain. The formation of Li pair complexes is the main obstacle to realize p-type conductance in Li doped ZnO. However, the formation energy of Lizn decreases as environment changes from Zn-rich to O-rich and becomes more stable than that of Li-pair complexes at highly O-rich environment. Therefore, p-type conductance can be obtained by Li doped ZnO grown or post annealed in oxygen rich atmosphere.
基金supported by the Ministry of Science and Technology(MOST)of China(Nos.2012CB932704,2012CB933001)the National Natural Science Foundation of China(NSFC,Nos.11274380,91433103,21173058,11622437,61674171 and 21203038)supported by the Outstanding Innovative Talents Cultivation Funded Programs 2015 of Renmin University of China
文摘It has been demonstrated that intermolecular interaction,crucial in a plenty of chemical and physical processes,may vary in the presence of metal surface.However,such modification is yet to be quantitatively revealed.Here,we present a systematical density functional theory study on adsorbed bis（para-pyridyl）acetylene（BPPA） tetramer on Au（111） surface.We observed unusually high electron density between two head-to-head N atoms,an intermolecular ＂non-bonded＂ region,in adsorbed BPPA tetramer.This exceptional electron density originates from the wavefunction hybridization of the two compressed N lone-electron-pair states of two BPPA,as squeezed by a newly revealed N-Au-N threecenter bonding.This bond,together with the minor contribution from N...H-C intermolecular hydrogen bonding,shortens the N-N distance from over 4 A to 3.30 A and offers an attractive lateral interacting energy of 0.60 eV,effectively to a surface-confined in-plane pressure.The overlapped non-bonding vvavefunction hybridization arising from the effective pressure induced by the N-Au-N three-center bonding,as not been fully recognized in earlier studies,was manifested in non-contact Atomic Force Microscopy.
基金This work was supported by the National Natural Science Foundation of China （No.50476025）.
文摘A theoretical study on the reaction of aluminum with water in the gas phase was performed using the hybrid density functional B3LYP and QCISD（T） methods with the 6-311＋G（d,p） and the 6-311＋＋G（d,p） basis sets. The results show that there are three possible reaction pathways that involve four isomers, seven transition structures, and two possible products for the reaction of aluminum with water. The two most favorable reaction pathways were found, whose intermediates and products agreed quite well with experimental results. The enthalpy and Gibbs free energy change of the reaction between A1 and H2O at 298 and 2000 K were calculated. Some results are also in good agreement with the previous calculations or experimental results.
基金the National Natural Science Foundation of China(No.61275108)the Natural Science Foundation of Zhejiang province in China(Nos.LY15F050009 and Y111049)
文摘The crystal structure, band structure, density of states, Mulliken charge, bond population and optical properties for LiBi_（1-x）M_xO_3（M=V, Nb, and Ta） were investigated using hybrid density functional theory. It was found that LiBiO_3 doped with V, Nb, and Ta presented distinctly stronger covalent interactions in M-O（M=V, Nb, and Ta） than Bi-O, thus resulting in mild distortion of the structure and facilitating the separation of photogenerated carriers. Furthermore, the hybridizations of Bi-6s, M-d（M=V, Nb, and Ta） and O-2p widened the valence and conduction bands, which promoted transmission of photogenerated carriers in the band edge and thus caused better photocatalytic performance.
基金supported by the Henan Joint Funds of the National Natural Science Foundation of China(Grant Nos.U1304612 and U1404608)the National Natural Science Foundation of China(Grant Nos.51374132 and 11404175)+1 种基金the Special Fund for Theoretical Physics of China(Grant No.11247222)Nanyang Normal University Science Foundation,China(Grant Nos.ZX2012018 and ZX2013019)
文摘Using first-principles calculations, we investigate the two-dimensional arsenic nanosheet isolated from bulk gray arsenic. Its dynamical stability is confirmed by phonon calculations and molecular dynamics analyzing. The arsenic sheet is an indirect band gap semiconductor with a band gap of 2.21 e V in the hybrid HSE06 functional calculations. The valence band maximum（VBM） and the conduction band minimum（CBM） are mainly occupied by the 4p orbitals of arsenic atoms,which is consistent with the partial charge densities of VBM and CBM. The charge density of the VBM G point has the character of a π bond, which originates from p orbitals. Furthermore, tensile and compressive strains are applied in the armchair and zigzag directions, related to the tensile deformations of zigzag and armchair nanotubes, respectively. We find that the ultimate strain in zigzag deformation is 0.13, smaller than 0.18 of armchair deformation. The limit compressive stresses of single-layer arsenic along armchair and zigzag directions are-4.83 GPa and-4.76 GPa with corresponding strains of-0.15 and-0.14, respectively.
基金supported by the National Basic Research Program of China (Grant No. 2013CB632101)the National Natural Science Foundation of China (Grant Nos. 61222404 and 61474097)the Program of the Ministry of Education of China for Innovative Research Teams in Universities (Grant No. IRT13R54)
文摘The formation, structural and electronic properties of silicene oxides（SOs） that result from the oxidation of silicene on Ag（111） surface have been investigated in the framework of density functional theory（DFT）.It is found that the honeycomb lattice of silicene on the Ag（111） surface changes after the oxidation. SOs are strongly hybridized with the Ag（111） surface so that they possess metallic band structures. Charge accumulation between SOs and the Ag（111） surface indicates strong chemical bonding, which dramatically affects the electronic properties of SOs. When SOs are peeled off the Ag（111） surface, however, they may become semiconductors.
基金supported by the National Natural Science Foundation of China (21476024, 21576008, 91334203 and 91634116)the National Key Technology Support Program (2014BAE12B01)+2 种基金Beijing Municipal Science and Technology Project (Z151100003315005)the Fundamental Research Funds for the Central Universities (PYCC1705)the “Chemical Grid Project” of BUCT
文摘Hybrid density functional calculations was used to comprehensively study the electronic structure of S-,Snand Pb-monodoped and（Sn,S）-and（Pb,S）-codoped hexagonal WO_3（h-WO_3）in order to improve their visible light photocatalytic activity.Results indicate that the（Sn,S）-and（Pb,S）-codoped h-WO_3 can realize a significant band gap reduction and prevent the formation of empty states in the valence band of h-WO_3,while Sn/Pb-monodoped h-WO_3 cannot,because in（Sn,S）-and（Pb,S）-codoping,the S-doping introduces the fully occupied S 3p states in the forbidden band gap of h-WO_3 and the acceptor metals（Sn and Pb）would assist the coupling of the introduced S with its nearest O.In particular,the（Sn,S）-codoped h-WO_3 has the narrowest band gap of 1.85 eV and highest reducing ability among the doped case.Moreover,the calculated optical absorption spectra show that（Sn,S）-codoping can improve the visible light absorption.In short,these results indicate that the（Sn,S）-codoped h-WO_3 is a promising material in solar-driven water splitting.
