Cargnoni Fausto, Kuś Tomasz, Mella Massimo, Bartlett Rodney J
ISTM-CNR, Milano, Italy.
J Chem Phys. 2008 Nov 28;129(20):204307. doi: 10.1063/1.3020706.
We present an ab initio investigation on the ground state interaction potentials [potential energy surface (PES)] between helium and the group 11 metal atoms: copper, silver, and gold. To the best of our knowledge, there are no previous theoretical PESs proposed for Cu-He and Au-He, and a single one for Ag-He [Z. J. Jakubek and M. Takami, Chem. Phys. Lett. 265, 653 (1997)], computed about 10 years ago at MP2 level and significantly improved by our study. To reach a high degree of accuracy in the determination of the three M-He potentials (M=Cu,Ag,Au), we performed extensive series of test computations to establish the appropriate basis set, the theoretical method, and the computational scheme for these systems. For each M-He dimer we computed the PES at the CCSD(T) level of theory, starting from the reference unrestricted Hartree-Fock wave function. We described the inner shells with relativistic small core pseudopotentials, and we adopted high quality basis sets for the valence electrons. We also performed CCSDT computations in a limited set of M-He internuclear distances, adopting a medium-sized basis set, such as to define for each dimer a CCSD(T) to CCSDT correction term and to improve further the quality of the CCSD(T) interaction potentials. The Cu-He complex has minimum interaction energy (E(min)) of -28.4 microhartree at the internuclear distance of 4.59 A (R(min)), and the short-range repulsive wall starts at 4.04 A (R(E=0)). Quite interestingly, the PES of Ag-He is more attractive (E(min)=-33.8 microhartree) but presents nearly the same R(min) and R(E=0) values, 4.60 and 4.04 A, respectively. The interaction potential for Au-He is markedly deeper and shifted at shorter distances as compared to the lighter complexes, with E(min)=-69.6 microhartree, R(min)=4.09 A and R(E=0)=3.60 A. As a first insight in the structure of M-He(n) aggregates, we determined the rovibrational structure of the three M-He dimers. The Cu-He and Ag-He potentials support just few rotational excitations, while the Au-He PES admits also a bound vibrational excitation.
我们对氦与第11族金属原子（铜、银和金）之间的基态相互作用势（势能面，PES）进行了从头算研究。据我们所知，此前尚未有针对Cu-He和Au-He的理论PES被提出，而针对Ag-He的理论PES只有一个[Z. J. Jakubek和M. Takami，《化学物理快报》265, 653 (1997)]，它是大约10年前在MP2水平计算得到的，并且我们的研究对其有显著改进。为了在确定三个M-He势（M = Cu、Ag、Au）时达到高精度，我们进行了一系列广泛的测试计算，以确定这些体系合适的基组、理论方法和计算方案。对于每个M-He二聚体，我们从参考无限制哈特里-福克波函数出发，在CCSD(T)理论水平计算PES。我们用相对论小核赝势描述内层电子壳，对价电子采用高质量基组。我们还在有限的一组M-He核间距下进行了CCSDT计算，采用中等大小的基组，以便为每个二聚体定义一个从CCSD(T)到CCSDT的校正项，并进一步提高CCSD(T)相互作用势的质量。Cu-He络合物在核间距为4.59 Å（R(min)）时具有-28.4微哈特里的最小相互作用能（E(min)），短程排斥壁从4.04 Å（R(E = 0)）开始。非常有趣的是，Ag-He的PES更具吸引力（E(min) = -33.8微哈特里），但R(min)和R(E = 0)值几乎相同，分别为4.60 Å和4.04 Å。与较轻的络合物相比，Au-He的相互作用势明显更深且向更短距离移动，E(min) = -69.6微哈特里，R(min) = 4.09 Å，R(E = 0) = 3.60 Å。作为对M-He(n)聚集体结构的初步洞察，我们确定了三个M-He二聚体的振转结构。Cu-He和Ag-He的势仅支持少数转动激发，而Au-He的PES还允许一个束缚振动激发。
