Si_nH/Si_nH^-(n=3～8)的结构和电子亲合能的研究

Structures and Electron Affinities of the Silicon Hydrides Si_nH/Si_nH^-(n=3～8)

选用四种不同的密度泛函理论方法(B3LYP,B3P86,BLYP,BP86),在全电子的双ζ加极化加弥散函数基组(DZP++)下,对SinH/SinH-(n=3~8)体系进行研究,获得它们的基态结构和电子亲合能。预测Si3H/Si3H-,Si4H/Si4H-,Si5H/Si5H-,Si6H/Si6H-,Si7H/Si7H-和Si8H/Si8H-的基态结构分别为C2v(2B2)/C2v(1A1)氢桥结构,Cs(2A')/Cs(1A'),C2v(2B2)/C2v(1A1),C2v(2B2或2B1)/C4v(1A1),C5v(2A1)/C5v(1A1)和Cs(2A″)/C3v(1A1)。在电子亲合能方面,B3LYP方法预测的电子亲合能是最可靠的,预测Si3H,Si4H,Si5H,Si6H,Si7H和Si8H的电子亲合能分别为2.56,2.59,2.84,2.86,3.19和3.14eV。

Four different density functional theory (DFT) methods (B3LYP, B3P86, BLYP, and BP86) have been employed to predict the molecular structures and adiabatic electron affinities of the SinH/SinH- (n=3~8) species. The basis set used in this study is of double-ζ plus polarization quality with additional s- and p-type diffuse functions, labeled as DZP++. The ground states of Si3H/Si3H-, Si4H/Si4H-, Si5H/Si5H-, Si6H/Si6H-, Si7H/Si7H-, and Si8H/Si8H- are C2v(2B2)/C2v(1A1) H-bridged structures, Cs(1A′)/Cs(1A′), C2v(2B2)/C2v(1A1), C2v(2B2 or 2B1)/C4v(1A1), C5v(2A1)/C5v(1A1), and Cs(2A″)/C3v(1A1), respectively. Compared with the experimental values, the B3LYP in all of these schemes is the best in respect of predicting electron affinities. The electron affinities corrected by zero-point vibrational energies for Si3H, Si4H, Si5H, Si6H, Si7H, and Si8H are 2.56, 2.59, 2.84, 2.86, 3.19, and 3.14 eV, respectively.