Doping is an effective way to improve the activity of photocatalysts.The effect of doping on the magnetic properties of some photocatalysts that are easily recycled was studied using the local spin density approximati...Doping is an effective way to improve the activity of photocatalysts.The effect of doping on the magnetic properties of some photocatalysts that are easily recycled was studied using the local spin density approximation(LSDA)+U method on typical divalent metal oxide semiconductors CuO,NiO,Ni‐doped CuO,and Cu‐doped NiO.It is found that the influence of Ni doping on the spatial structure of CuO and that of Cu doping on the spatial structure of NiO are negligible because of the similar radii of Ni2+and Cu2+.The valence band and conduction band for Ni‐doped CuO are clearly spin‐split,corresponding to a net effective magnetic moment ofμeff=1.66μB.This may improve the photocatalytic efficiency and raise the recycle rate of photocatalysts.In the Cu‐doped NiO system,the presence of Cu3d states near to the Fermi level increases the width of the valence band and narrows the band gap with respect to that in pure NiO.Beyond the Cu3d states,within the band gap,appear two energy levels around the Fermi level,which may effectively separate the electron‐hole pair and also lead to enhanced absorption of visible light and infrared light.It can be concluded that the observed changes in the band structure may be helpful for improving the activity of photocatalysts and the doped systems have net magnetic moments,meaning that they are easily recycled and can be reused.展开更多
We perform first-principles calculations of crystal structure,magnetism,electronic structure,chemical bonding and elastic properties for PuC_2 using the standard local spin-density approximation(LSDA)+U scheme.The use...We perform first-principles calculations of crystal structure,magnetism,electronic structure,chemical bonding and elastic properties for PuC_2 using the standard local spin-density approximation(LSDA)+U scheme.The use of the Hubbard term to describe the 5f electrons of plutonium is discussed according to the lattice parameters,magnetism and densities of states.Our calculated lattice constants and magnetism are in good agreement with the experimental data or other theoretical calculations.It is shown that the total densities of states at the Fermi energy level mainly come from the contribution of narrow f band.The Pu-C bonds of PuC_2 have a mixture of covalent character and ionic character,while covalent character is stronger than ionic character.The C1-C2 bonding has strong covalent character because of sp^2 hybridization between C atoms.Lastly,the elastic properties of PuC_2 are studied.We hope that our results can provide a useful reference for further theoretical and experimental research on PuC_2.展开更多
A first-principles study of structure property correlation and the origin of ferrimagnetism is presented based on LSDA+U method. In particular, the results for the ground state structure, electronic band structure, de...A first-principles study of structure property correlation and the origin of ferrimagnetism is presented based on LSDA+U method. In particular, the results for the ground state structure, electronic band structure, density of states, Born effective charges, spontaneous polarization and cationic disorder are discussed. The calculations were done using Vienna ab-initio simulation package (VASP) with projector augmented wave method. We find that the ground state structure is orthorhombic and insulating having A-type antiferromagnetic spin configuration. The cationic disorder is found to play an important role. Although the cationic site disorder is not spontaneous in the ground state, interchange of octahedrally coordinated Ga2 and Fe2 sites is most favored. We find that ferrimagnetism? in gallium ferrite is primarily due to this exchange between Ga-Fe sites? such that Fe spins at Ga1 and Ga2 sites are antiferromagnetically aligned? while maintaining ferromagnetic coupling between Fe spins at Ga1 and Fe1? sites as well as between Fe spins at Ga2 and Fe2 sites. Further, the partial density of states shows noticeable hybridization of Fe 3d, Ga 4s,? Ga 4p and O 2p states indicating some covalent character of Ga/Fe-O bonds.? However, the charge density and electron localization functions show largely the ionic character of these bonds. Our calculation predicts spontaneous polarization of ~59 μC/cm2 along b-axis.展开更多
基金supported by the National Natural Science Foundation of China(21377044,11304234,21573085)the Key Project of Natural Science Foundation of Hubei Province(2015CFA037)~~
文摘Doping is an effective way to improve the activity of photocatalysts.The effect of doping on the magnetic properties of some photocatalysts that are easily recycled was studied using the local spin density approximation(LSDA)+U method on typical divalent metal oxide semiconductors CuO,NiO,Ni‐doped CuO,and Cu‐doped NiO.It is found that the influence of Ni doping on the spatial structure of CuO and that of Cu doping on the spatial structure of NiO are negligible because of the similar radii of Ni2+and Cu2+.The valence band and conduction band for Ni‐doped CuO are clearly spin‐split,corresponding to a net effective magnetic moment ofμeff=1.66μB.This may improve the photocatalytic efficiency and raise the recycle rate of photocatalysts.In the Cu‐doped NiO system,the presence of Cu3d states near to the Fermi level increases the width of the valence band and narrows the band gap with respect to that in pure NiO.Beyond the Cu3d states,within the band gap,appear two energy levels around the Fermi level,which may effectively separate the electron‐hole pair and also lead to enhanced absorption of visible light and infrared light.It can be concluded that the observed changes in the band structure may be helpful for improving the activity of photocatalysts and the doped systems have net magnetic moments,meaning that they are easily recycled and can be reused.
基金the National Natural Science Foundation of China under Grant Nos.21371160,21401173the Science Challenge Program of China
文摘We perform first-principles calculations of crystal structure,magnetism,electronic structure,chemical bonding and elastic properties for PuC_2 using the standard local spin-density approximation(LSDA)+U scheme.The use of the Hubbard term to describe the 5f electrons of plutonium is discussed according to the lattice parameters,magnetism and densities of states.Our calculated lattice constants and magnetism are in good agreement with the experimental data or other theoretical calculations.It is shown that the total densities of states at the Fermi energy level mainly come from the contribution of narrow f band.The Pu-C bonds of PuC_2 have a mixture of covalent character and ionic character,while covalent character is stronger than ionic character.The C1-C2 bonding has strong covalent character because of sp^2 hybridization between C atoms.Lastly,the elastic properties of PuC_2 are studied.We hope that our results can provide a useful reference for further theoretical and experimental research on PuC_2.
文摘A first-principles study of structure property correlation and the origin of ferrimagnetism is presented based on LSDA+U method. In particular, the results for the ground state structure, electronic band structure, density of states, Born effective charges, spontaneous polarization and cationic disorder are discussed. The calculations were done using Vienna ab-initio simulation package (VASP) with projector augmented wave method. We find that the ground state structure is orthorhombic and insulating having A-type antiferromagnetic spin configuration. The cationic disorder is found to play an important role. Although the cationic site disorder is not spontaneous in the ground state, interchange of octahedrally coordinated Ga2 and Fe2 sites is most favored. We find that ferrimagnetism? in gallium ferrite is primarily due to this exchange between Ga-Fe sites? such that Fe spins at Ga1 and Ga2 sites are antiferromagnetically aligned? while maintaining ferromagnetic coupling between Fe spins at Ga1 and Fe1? sites as well as between Fe spins at Ga2 and Fe2 sites. Further, the partial density of states shows noticeable hybridization of Fe 3d, Ga 4s,? Ga 4p and O 2p states indicating some covalent character of Ga/Fe-O bonds.? However, the charge density and electron localization functions show largely the ionic character of these bonds. Our calculation predicts spontaneous polarization of ~59 μC/cm2 along b-axis.
