Lantto Perttu, Vaara Juha
NMR Research Group, Department of Physical Sciences, P.O. Box 3000, FIN-90014 University of Oulu, Finland.
J Chem Phys. 2006 Nov 7;125(17):174315. doi: 10.1063/1.2363371.
The nuclear quadrupole coupling constants (NQCCs) of noble gas and noble metal nuclei in the recently found noble gas-noble metal fluorides (NgMF, where Ng=Ar,Kr,Xe and M=Cu,Ag,Au) are obtained theoretically by high-level ab initio calculations, where both relativistic and electron correlation effects are included, and compared to experimental results. Fully relativistic four-component Dirac-Hartree-Fock (DHF) calculations are carried out at the basis set limit for electric field gradient that couples with the electric quadrupole moment of the nucleus, and uncorrelated relativistic effects are extracted by comparing DHF results to nonrelativistic (NR) HF calculations. Electron correlation effects are investigated both at fully relativistic second-order Moller-Plesset (DMP2) and at NR MP2 levels of theory, as well as at the NR coupled-cluster singles and doubles with perturbational triples [CCSD(T)] level. The validity of the approximation where relativistic effects, on the one hand, and nonrelativistically obtained correlation effects, on the other hand, are evaluated separately and assumed to be additive, is investigated by comparison with the DMP2 results. Inclusion of relativistic effects is shown to be necessary for obtaining the correct NQCC trends as the nucleus of interest and/or its neighbors become heavier. Electron correlation treatment is needed for approaching quantitative agreement with the experimental NQCCs. The assumption of additive electron correlation and relativistic effects, corresponding to the NR correlation treatment added on top of relativistic DHF data, gives qualitatively correct noble gas NQCCs. For noble metal NQCCs, correlation treatment at the relativistic level of theory is mandatory for reaching agreement with experimental results. Current work also confirms the experimental trends of NQCCs, which have been taken as an indication of nearly covalent interaction between noble gas and noble metal in the heaviest present systems, especially in XeAuF.
通过高水平的从头算计算理论上获得了最近发现的稀有气体 - 贵金属氟化物（NgMF，其中Ng = Ar、Kr、Xe且M = Cu、Ag、Au）中稀有气体和贵金属原子核的核四极耦合常数（NQCCs），计算中包含了相对论效应和电子相关效应，并与实验结果进行了比较。在与原子核电四极矩耦合的电场梯度的基组极限下进行了全相对论四分量狄拉克 - 哈特里 - 福克（DHF）计算，并通过将DHF结果与非相对论（NR）HF计算进行比较来提取非相关相对论效应。在全相对论二阶莫勒 - 普莱塞特（DMP2）以及NR MP2理论水平上，以及在NR耦合簇单双激发加微扰三重激发[CCSD(T)]水平上研究了电子相关效应。通过与DMP2结果比较，研究了一方面相对论效应和另一方面非相对论获得的相关效应分别评估并假定为可加性的近似的有效性。结果表明，随着感兴趣的原子核和/或其相邻原子核变重，包含相对论效应对于获得正确的NQCC趋势是必要的。需要进行电子相关处理才能在数量上与实验NQCCs达成一致。对应于在相对论DHF数据之上添加NR相关处理的电子相关和相对论效应的可加性假设，给出了定性正确的稀有气体NQCCs。对于贵金属NQCCs，在相对论理论水平上进行相关处理对于与实验结果达成一致是必不可少的。当前的工作还证实了NQCCs的实验趋势，这被视为在目前最重的体系中，特别是在XeAuF中，稀有气体和贵金属之间近乎共价相互作用的一个迹象。
