Excess electrons are not only an important source of radiation damage,but also participate in the repair process of radiation damage such as cyclobutane pyrimidine dimer(CPD).Using ab initio molecular dynamics(AIMD)si...Excess electrons are not only an important source of radiation damage,but also participate in the repair process of radiation damage such as cyclobutane pyrimidine dimer(CPD).Using ab initio molecular dynamics(AIMD)simulations,we reproduce the single excess electron stepwise catalytic CPD dissociation process in detail with an emphasis on the energy levels and molecular structure details associated with excess electrons.On the basis of the AIMD simulations on the CPD aqueous solution with two vertically added excess electrons,we exclude the early-proposed[2+2]-like concerted synchronous dissociation mechanism,and analyze the difference between the symmetry of the actual reaction and the symmetry of the frontier molecular orbitals which deeply impact the mechanism.Importantly,we propose a new model of the stepwise electron-catalyzed dissociation mechanism that conforms to the reality.This work not only provides dynamics insights into the excess electron catalyzed dissociation mechanism,but also reveals different roles of two excess electrons in two bond-cleavage steps(promoting versus inhibiting).展开更多
The present study supports the provocative idea that the nucleus directs the atom’s electronic structure. With the progress of the atomic number the Atomic Molar Volume evolution of the chemical elements obeys the a...The present study supports the provocative idea that the nucleus directs the atom’s electronic structure. With the progress of the atomic number the Atomic Molar Volume evolution of the chemical elements obeys the atom’s electronic structure rules, fitting at the same time the concomitant specular evolution of the Neutron Excess addition to the nuclei. Details such as the Atomic Molar Volume contraction of the d blocks transition metals or of the Eu and Yb atomic volume anomaly of the lanthanoid metals respond to the nuclear in addition to the atom’s electronic structure. Atom’s nuclei are synthetized in the star interior and capture the electrons only after migration to the star’s periphery, to become stable atoms: nuclei are prior to atoms. Nuclear structure elements, like the 50 and 82 neutron and proton magic numbers, are geared to the noble gases, the central elements of the electronic structure.展开更多
Oxygen vacancy （Ov） has significant influence on physical and chemical properties of TiO2 systems, especially on surface catalytic processes. In this work, we investigate the effects of Ov on the adsorption of forma...Oxygen vacancy （Ov） has significant influence on physical and chemical properties of TiO2 systems, especially on surface catalytic processes. In this work, we investigate the effects of Ov on the adsorption of formaldehyde （HCHO） on TiO2（110） surfaces through first- principles calculations. With the existence of Ov, we find the spatial distribution of surface excess charge can change the relative stability of various adsorption configurations. In this case, the bidentate adsorption at five-coordinated Ti （Tisc） can be less stable than the monodentate adsorption. And HCHO adsorbed in Ov becomes the most stable structure. These results are in good agreement with experimental observations, which reconcile the long-standing deviation between the theoretical prediction and experimental results. This work brings insights into how the excess charge affects the molecule adsorption on metal oxide surface.展开更多
Defect engineering is in the limelight for the fabrication of electrochemical energy storage devices.However,determining the influence of the defect density and location on the electrochemical behavior remains challen...Defect engineering is in the limelight for the fabrication of electrochemical energy storage devices.However,determining the influence of the defect density and location on the electrochemical behavior remains challenging.Herein,self-organized TiO_(2)nanotube arrays(TNTAs)are synthesized by anodization,and their oxygen defect location and density are tuned by a controllable post-annealing process.TNTAs annealed at 600℃ in N2 exhibit the highest capacity(289.2 m Ah g^(-1)at 0.8 C)for lithium-ion storage,while those annealed at 900℃ in N2 show a specific capacitance of 35.6 m F cm^(-2)and stability above96%after 10,000 cycles for supercapacitor.Ex situ electron paramagnetic resonance spectra show that the surface-exposed oxygen defects increase,but the bulk embedded oxygen defects decrease with increasing annealing temperature.Density functional theory simulations reveal that a higher density of bulk oxygen defects corresponds to higher localized electrons states,which upshift the Fermi level and facilitate the lithium intercalation kinetic process.Meanwhile,differential charge density calculation indicates that the increase of surface oxygen defects in the anatase(101)plane leads to higher density excess electrons,which act as negative charge centers to enhance the surface potential for ion adsorption.This oxygen-deficient location and density tunable strategy introduce new opportunities for high-energy and high-power-density energy storage systems.展开更多
基金supported by the National Natural Science Foundation of China(No.21873056,No.21773137,and No.21573128)。
文摘Excess electrons are not only an important source of radiation damage,but also participate in the repair process of radiation damage such as cyclobutane pyrimidine dimer(CPD).Using ab initio molecular dynamics(AIMD)simulations,we reproduce the single excess electron stepwise catalytic CPD dissociation process in detail with an emphasis on the energy levels and molecular structure details associated with excess electrons.On the basis of the AIMD simulations on the CPD aqueous solution with two vertically added excess electrons,we exclude the early-proposed[2+2]-like concerted synchronous dissociation mechanism,and analyze the difference between the symmetry of the actual reaction and the symmetry of the frontier molecular orbitals which deeply impact the mechanism.Importantly,we propose a new model of the stepwise electron-catalyzed dissociation mechanism that conforms to the reality.This work not only provides dynamics insights into the excess electron catalyzed dissociation mechanism,but also reveals different roles of two excess electrons in two bond-cleavage steps(promoting versus inhibiting).
文摘The present study supports the provocative idea that the nucleus directs the atom’s electronic structure. With the progress of the atomic number the Atomic Molar Volume evolution of the chemical elements obeys the atom’s electronic structure rules, fitting at the same time the concomitant specular evolution of the Neutron Excess addition to the nuclei. Details such as the Atomic Molar Volume contraction of the d blocks transition metals or of the Eu and Yb atomic volume anomaly of the lanthanoid metals respond to the nuclear in addition to the atom’s electronic structure. Atom’s nuclei are synthetized in the star interior and capture the electrons only after migration to the star’s periphery, to become stable atoms: nuclei are prior to atoms. Nuclear structure elements, like the 50 and 82 neutron and proton magic numbers, are geared to the noble gases, the central elements of the electronic structure.
文摘Oxygen vacancy （Ov） has significant influence on physical and chemical properties of TiO2 systems, especially on surface catalytic processes. In this work, we investigate the effects of Ov on the adsorption of formaldehyde （HCHO） on TiO2（110） surfaces through first- principles calculations. With the existence of Ov, we find the spatial distribution of surface excess charge can change the relative stability of various adsorption configurations. In this case, the bidentate adsorption at five-coordinated Ti （Tisc） can be less stable than the monodentate adsorption. And HCHO adsorbed in Ov becomes the most stable structure. These results are in good agreement with experimental observations, which reconcile the long-standing deviation between the theoretical prediction and experimental results. This work brings insights into how the excess charge affects the molecule adsorption on metal oxide surface.
基金supported by the National Nature Science Foundation of China(11575025,U1832176)the Science and Technology Project of Beijing(Z171100002017008)the Fundamental Research Funds for the Central Universities。
文摘Defect engineering is in the limelight for the fabrication of electrochemical energy storage devices.However,determining the influence of the defect density and location on the electrochemical behavior remains challenging.Herein,self-organized TiO_(2)nanotube arrays(TNTAs)are synthesized by anodization,and their oxygen defect location and density are tuned by a controllable post-annealing process.TNTAs annealed at 600℃ in N2 exhibit the highest capacity(289.2 m Ah g^(-1)at 0.8 C)for lithium-ion storage,while those annealed at 900℃ in N2 show a specific capacitance of 35.6 m F cm^(-2)and stability above96%after 10,000 cycles for supercapacitor.Ex situ electron paramagnetic resonance spectra show that the surface-exposed oxygen defects increase,but the bulk embedded oxygen defects decrease with increasing annealing temperature.Density functional theory simulations reveal that a higher density of bulk oxygen defects corresponds to higher localized electrons states,which upshift the Fermi level and facilitate the lithium intercalation kinetic process.Meanwhile,differential charge density calculation indicates that the increase of surface oxygen defects in the anatase(101)plane leads to higher density excess electrons,which act as negative charge centers to enhance the surface potential for ion adsorption.This oxygen-deficient location and density tunable strategy introduce new opportunities for high-energy and high-power-density energy storage systems.
