Department of Physics, Washington State University, Richland, Washington 99354, USA.
J Chem Phys. 2010 Mar 21;132(11):114306. doi: 10.1063/1.3356046.
The effects of isoelectronic substitution on the electronic and structural properties of gold clusters are investigated in the critical size range of the two-dimensional (2D)-three-dimensional (3D) structural transition (MAu(n)(-), n=8-11; M=Ag,Cu) using photoelectron spectroscopy and density functional calculations. Photoelectron spectra of MAu(n)(-) are found to be similar to those of the bare gold clusters Au(n+1)(-), indicating that substitution of a Au atom by a Ag or Cu atom does not significantly alter the geometric and electronic structures of the clusters. The only exception occurs at n=10, where very different spectra are observed for MAu(10)(-) from Au(11)(-), suggesting a major structural change in the doped clusters. Our calculations confirm that MAu(8)(-) possesses the same structure as Au(9)(-) with Ag or Cu simply replacing one Au atom in its C(2v) planar global minimum structure. Two close-lying substitution isomers are observed, one involves the replacement of a center Au atom and another one involves an edge site. For Au(10)(-) we identify three coexisting low-lying planar isomers along with the D(3h) global minimum. The coexistence of so many low-lying isomers for the small-sized gold cluster Au(10)(-) is quite unprecedented. Similar planar structures and isomeric forms are observed for the doped MAu(9)(-) clusters. Although the global minimum of Au(11)(-) is planar, our calculations suggest that only simulated spectra of 3D structures agree with the observed spectra for MAu(10)(-). For MAu(11)(-), only a 3D isomer is observed, in contrast to Au(12)(-) which is the critical size for the 2D-3D structural transition with both the 2D and 3D isomers coexisting. The current work shows that structural perturbations due to even isoelectronic substitution of a single Au atom shift the 2D to 3D structural transition of gold clusters to a smaller size.
采用光电子能谱和密度泛函计算方法，在二维（2D）-三维（3D）结构转变的关键尺寸范围内（MAu(n)(-), n=8-11; M=Ag,Cu），研究等电子取代对金团簇的电子和结构性质的影响。发现 MAu(n)(-)的光电子能谱与裸露的金团簇 Au(n+1)(-)的光电子能谱相似，表明用 Ag 或 Cu 取代一个 Au 原子不会显著改变团簇的几何和电子结构。唯一的例外发生在 n=10 处，对于 MAu(10)(-)，观察到与 Au(11)(-)非常不同的光谱，表明掺杂团簇发生了重大结构变化。我们的计算证实，MAu(8)(-)具有与 Au(9)(-)相同的结构，Ag 或 Cu 只是在其 C(2v)平面全局最小结构中取代一个 Au 原子。观察到两个紧密排列的取代异构体，一个涉及取代中心 Au 原子，另一个涉及边缘位置。对于 Au(10)(-)，我们确定了三种共存的低能平面异构体以及 D(3h)全局最小结构。对于小尺寸金团簇 Au(10)(-)，共存如此多的低能异构体是前所未有的。掺杂的 MAu(9)(-)团簇也观察到类似的平面结构和异构形式。尽管 Au(11)(-)的全局最小是平面的，但我们的计算表明，只有模拟的 3D 结构的光谱与 MAu(10)(-)的观察光谱一致。对于 MAu(11)(-)，仅观察到一个 3D 异构体，而 Au(12)(-)是 2D-3D 结构转变的关键尺寸，2D 和 3D 异构体共存。目前的工作表明，即使是单个 Au 原子的等电子取代引起的结构扰动也会将金团簇的 2D-3D 结构转变推向更小的尺寸。
