二缺位γ-Keggin型多金属氧酸盐电子性质的密度泛函理论研究

Density Functional Theory Studies on the Electronic Properties of Dilacunary γ-Keggin Polyoxometalate Anions

采用密度泛函理论(DFT)方法研究了二缺位γ-Keggin型[γ-Xn+W10O36](12-n)-(X=AlⅢ,SiⅣ,PⅤ,SⅥ,GaⅢ,GeⅣ,AsⅤ,SeⅥ)阴离子的几何结构和电子性质.结果表明,在二缺位γ-Keggin型阴离子中,中心四面体氧原子Oa与中心杂原子及钨原子间的键长[d(X—Oa)及d(W—Oa)]随中心杂原子的变化而改变,这与中心杂原子的半径有关.而中心四面体XO4所占据的空穴大小并不因中心杂原子X的改变而有明显变化.各体系的最高占有轨道(HOMO)主要由桥氧的p轨道构成.除[γ-SeW10O36]6-外,各体系的最低空轨道(LUMO)主要由钨原子的d轨道组成.中心杂原子X对二缺位γ-Keggin型阴离子的HOMO和LUMO能级起决定作用,对于中心杂原子为同周期元素的体系,随着杂原子的原子序数增大,体系的LUMO能级依次降低.

The geometrical structures and electronic properties of dilacunary T-Keggin polyanions [y-X^n＋ W10O36 ] {12-n}- （X = Al^II, Si^IV , p^V, S^VI Ga^IV, Ge^IV , As^V Se^VI） were investigated via density functional theory（DFT） methods. The results show that the bond lengths between central tetrahedral oxygen atom O o and central heteroatom X, as well as tungsten atom depend on the central heteroatom X. However, the sizes of XO4 are independent with the central heteroatom. The highest occupied molecular orbital（HOMO） of [ y-Xn＋ W10O36 ] （12 -n） mainly concentrates on the bridge oxygen atoms. Except for [ y-SeW10 O36 ] 6-, the lowest unoccupied molecular orbital（LUMO） of polyanion is from d orbitals of tungsten atoms. The energies of HOMO and LUMO of [y-X^n＋W10O36]（12-n）- depend on the central heteroatom X. The LUMO energy decreases with the increasing of the atomic numbers, and the central atoms are in the same row in periodic table.