Department of Chemistry, University of Washington, Seattle, Washington 98195, United States.
William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States.
J Phys Chem Lett. 2021 Aug 12;12(31):7574-7582. doi: 10.1021/acs.jpclett.1c01884. Epub 2021 Aug 4.
We present benchmark binding energies of naturally occurring gas molecules CH, CO, and HS in the small cage, namely, the pentagonal dodecahedron (5) (HO), which is one of the constituent cages of the 3 major lattices (structures I, II, and H) of clathrate hydrates. These weak interactions require higher levels of electron correlation and converge slowly with an increasing basis set to the complete basis set (CBS) limit, necessitating the use of large basis sets up to the aug-cc-pV5Z and subsequent correction for basis set superposition error (BSSE). For the host hollow (HO) cages, we have identified a most stable isomer with binding energy of -200.8 ± 2.1 kcal/mol at the CCSD(T)/CBS limit (-199.2 ± 0.5 kcal/mol at the MP2/CBS limit). Additionally, we report converged second order Møller-Plesset (MP2) CBS binding energies for the encapsulation of guests in the (HO) cage of -4.3 ± 0.1 for CH@(HO), -6.6 ± 0.1 for CO@(HO), and -8.5 ± 0.1 kcal/mol for HS@(HO), respectively. For CH@(HO), exhibiting the weakest encapsulation affinity among the three, we report CCSD(T)/aug-cc-pVTZ binding energies and, based on them, a CCSD(T)/CBS estimate of -4.75 ± 0.1 kcal/mol. To the best of our knowledge, the CCSD(T)/aug-cc-pVTZ calculation for CH@(HO) is the largest one reported to date (168 valence electrons, 1978 basis functions, and the correlation of 84 doubly occupied and 1873 virtual orbitals) and required a scalable implementation of the (T) module on 6144 nodes (350 208 cores) of the "Cori" supercomputer at the National Energy Research Supercomputing Center (NERSC) for a total execution time of 195 min (for the (T) part). These efficient scalable implementations of highly correlated methods offer the capability to obtain long-lasting benchmarks of intermolecular interactions in complex systems. They also provide a path toward parametrizing classical potentials needed to study the dynamical and transport properties in these complex systems as well as assess the accuracy of lower scaling electronic structure methods such as density functional theory (DFT) and MP2 including its spin-biased variants.
我们呈现了自然存在的气体分子 CH、CO 和 HS 在小笼中的基准结合能，即五元十二面体（5）（HO），它是水合物笼状结构的 3 种主要晶格（结构 I、II 和 H）的组成笼之一。这些弱相互作用需要更高水平的电子相关，并且随着基组的增加，收敛速度缓慢，直到达到完全基组（CBS）极限，因此需要使用大基组，直到 aug-cc-pV5Z，并随后对基组叠加误差（BSSE）进行修正。对于主体空笼（HO）笼，我们确定了最稳定的异构体，其结合能在 CCSD(T)/CBS 极限下为-200.8 ± 2.1 kcal/mol（在 MP2/CBS 极限下为-199.2 ± 0.5 kcal/mol）。此外，我们报告了在（HO）笼中封装客体的收敛二阶 Møller-Plesset（MP2）CBS 结合能，分别为-4.3 ± 0.1 kcal/mol 用于 CH@(HO)、-6.6 ± 0.1 kcal/mol 用于 CO@(HO)和-8.5 ± 0.1 kcal/mol 用于 HS@(HO)。对于 CH@(HO)，它表现出三种客体中最弱的封装亲和力，我们报告了 CCSD(T)/aug-cc-pVTZ 结合能，并基于这些结合能，对 CCSD(T)/CBS 的估计值为-4.75 ± 0.1 kcal/mol。据我们所知，CH@(HO)的 CCSD(T)/aug-cc-pVTZ 计算是迄今为止报道的最大计算（168 个价电子，1978 个基函数，以及 84 个双占据轨道和 1873 个虚拟轨道的相关性），并且需要在国家能源研究超级计算中心（NERSC）的“Cori”超级计算机上的 6144 个节点（350 208 核）上实现（T）模块的可扩展实现，总执行时间为 195 分钟（对于（T）部分）。这些高效的可扩展相关方法的实现提供了获得复杂系统中分子间相互作用的持久基准的能力。它们还为研究这些复杂系统中的动力学和输运性质以及评估密度泛函理论（DFT）和 MP2 等较低缩放电子结构方法的准确性（包括其自旋偏置变体）所需的经典势参数化提供了途径。
