The structural characteristic and electronic properties of seven WO_3 bulk polymorphs have been studied by first-principles density functional theory(DFT) calculations. Our calculation results indicate that according ...The structural characteristic and electronic properties of seven WO_3 bulk polymorphs have been studied by first-principles density functional theory(DFT) calculations. Our calculation results indicate that according to the energy of WO_3 per unit, the stability of different WO_3 systems reduces in turn in the following order: monoclinic WO_3, orthorhombic WO_3, tetragonal WO_3, triclinic WO_3, hexagonal WO_3 and cubic WO_3. And when the unit cell is distorted from the cubic framework, the alternatively long and short W–O bonds are formed, implying an improvement of bonding-antibonding splitting associated with the interactions between W and O atoms. The deformation of the WO6 octahedron enhances the stability of the system to some extent though the energy difference between various WO_3 phases is small(< 0.1 eV/per WO_3 unit). Besides, the band gap tends to enlarge accompanied with the symmetry decrease of WO_3 bulk. According to the band structures, the minimum band gaps for those WO_3 polymorphs are direct at the Γ point except for the simple cubic and hexagonal structures. In addition, for all the WO_3 phases, the compositions of the valance band maximum(VBM) and conduction band minimum(CBM) are the same, which are relative to the O 2 p and W 5 d orbitals, respectively.展开更多
基金supported by the National Natural Science Foundation of China(21563030 and 21773030)the Jiangxi Provincial Department of Education Research Fund(12698)the Independent Research Project of State Key Laboratory of Photocatalysis on Energy and Environment(2014A02)
文摘The structural characteristic and electronic properties of seven WO_3 bulk polymorphs have been studied by first-principles density functional theory(DFT) calculations. Our calculation results indicate that according to the energy of WO_3 per unit, the stability of different WO_3 systems reduces in turn in the following order: monoclinic WO_3, orthorhombic WO_3, tetragonal WO_3, triclinic WO_3, hexagonal WO_3 and cubic WO_3. And when the unit cell is distorted from the cubic framework, the alternatively long and short W–O bonds are formed, implying an improvement of bonding-antibonding splitting associated with the interactions between W and O atoms. The deformation of the WO6 octahedron enhances the stability of the system to some extent though the energy difference between various WO_3 phases is small(< 0.1 eV/per WO_3 unit). Besides, the band gap tends to enlarge accompanied with the symmetry decrease of WO_3 bulk. According to the band structures, the minimum band gaps for those WO_3 polymorphs are direct at the Γ point except for the simple cubic and hexagonal structures. In addition, for all the WO_3 phases, the compositions of the valance band maximum(VBM) and conduction band minimum(CBM) are the same, which are relative to the O 2 p and W 5 d orbitals, respectively.
