Chemistry Department, The University of Alabama, Shelby Hall, Box 870336, Tuscaloosa, Alabama 35487-0336, USA.
J Phys Chem A. 2010 Feb 25;114(7):2665-83. doi: 10.1021/jp910310j.
The group IVB transition-metal dioxide clusters and their anions, (MO(2))(n) and (MO(2))(n)(-) (M = Zr, Hf; n = 1-4), are studied with coupled cluster (CCSD(T)) theory and density functional theory (DFT). Similar to the results for M = Ti, these oxide clusters have a number of low-lying isomeric structures, which can make it difficult to predict the ground electronic state especially for the anion. Electron affinities for the low-lying structures are calculated and compared with those for M = Ti. Electron affinities of these clusters depend strongly on the cluster structures. Anion photoelectron spectra are calculated for the monomer and dimer and demonstrate the possibility for structural identification at a spectral line width of <or=0.05 eV. Electron excitation energies from the low-lying states to the singlet and triplet excited states are calculated self-consistently, as well as by the time-dependent DFT and equation-of-motion coupled cluster (EOM-CCSD) methods. The calculated excitation energies are compared to the band energies of bulk oxides, indicating that the excitation energy is not yet converged for n = 4 for these clusters. The excitation energies of the low-lying isomeric clusters are less than the bulk metal oxide band gaps and suggest that these clusters could be useful photocatalysts with a visible light source.
我们采用耦合簇（CCSD(T)）理论和密度泛函理论（DFT）研究了第 IVB 过渡金属二氧化物团簇及其阴离子（MO(2))(n) 和 (MO(2))(n)(-)（M = Zr，Hf；n = 1-4）。与 M = Ti 的结果相似，这些氧化物团簇具有许多低能异构结构，这使得很难预测基态电子态，尤其是对于阴离子。我们计算了低能结构的电子亲和能，并与 M = Ti 的电子亲和能进行了比较。这些团簇的电子亲和能强烈依赖于团簇结构。我们计算了单体和二聚体的阴离子光电子能谱，并证明了在谱线宽度 < 0.05 eV 的情况下进行结构鉴定的可能性。我们还通过时间相关密度泛函理论（TD-DFT）和运动方程耦合簇（EOM-CCSD）方法自洽地计算了低能态到单重态和三重态激发态的电子激发能。将计算得到的激发能与体氧化物的能带能量进行了比较，表明这些团簇的 n = 4 激发能尚未收敛。低能异构团簇的激发能小于体金属氧化物的能带间隙，这表明这些团簇在可见光光源下可能是有用的光催化剂。
