Cui Li-Feng, Lin Ying-Chan, Sundholm Dage, Wang Lai-Sheng
Department of Physics, Washington State University, Richland, Washington 99354, USA.
J Phys Chem A. 2007 Aug 9;111(31):7555-61. doi: 10.1021/jp0703511. Epub 2007 May 10.
Negatively charged sodium auride clusters, NanAun- (n = 1-3), have been investigated experimentally using photoelectron spectroscopy and ab initio calculations. Well-resolved electronic transitions were observed in the photoelectron spectra of NanAun- (n = 1-3) at several photon energies. Very large band gaps were observed in the photoelectron spectra of the anion clusters, indicating that the corresponding neutral clusters are stable closed-shell species. Calculations show that the global minimum of Na2Au2- is a quasi-linear species with Cs symmetry. A planar isomer of D2h symmetry is found to be 0.137 eV higher in energy. The two lowest energy isomers of Na3Au3- consist of three-dimensional structures of Cs symmetry. The global minimum of Na3Au3- has a bent-flake structure lying 0.077 eV below a more compact structure. The global minima of the sodium auride clusters are confirmed by the good agreement between the calculated electron detachment energies of the anions and the measured photoelectron spectra. The global minima of neutral Na2Au2 and Na3Au3 are found to possess higher symmetries with a planar four-membered ring (D2h) and a six-membered ring (D3h) structure, respectively. The chemical bonding in the sodium auride clusters is found to be highly ionic with Au acting as the electron acceptor.
带负电荷的钠金簇合物NanAun-（n = 1 - 3）已通过光电子能谱和从头算进行了实验研究。在几个光子能量下，在NanAun-（n = 1 - 3）的光电子能谱中观察到了分辨良好的电子跃迁。在阴离子簇的光电子能谱中观察到非常大的带隙，这表明相应的中性簇是稳定的闭壳层物种。计算表明，Na2Au2-的全局最小值是具有Cs对称性的准线性物种。发现D2h对称性的平面异构体能量高0.137 eV。Na3Au3-的两个最低能量异构体由具有Cs对称性的三维结构组成。Na3Au3-的全局最小值具有弯曲片状结构，比更紧凑的结构低0.077 eV。通过计算阴离子的电子脱离能与测量的光电子能谱之间的良好一致性，证实了钠金簇的全局最小值。发现中性Na2Au2和Na3Au3的全局最小值分别具有更高的对称性，具有平面四元环（D2h）和六元环（D3h）结构。发现钠金簇中的化学键具有高度离子性，其中Au充当电子受体。
