Shi Benjamin X, Della Pia Flaviano, Al-Hamdani Yasmine S, Michaelides Angelos, Alfè Dario, Zen Andrea
Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
Dipartimento di Fisica Ettore Pancini, Universita di Napoli Federico II, Monte Sant'Angelo, I-80126 Napoli, Italy.
J Chem Phys. 2025 Apr 14;162(14). doi: 10.1063/5.0254021.
The accurate treatment of noncovalent interactions is necessary to model a wide range of applications, from molecular crystals to surface catalysts to aqueous solutions and many more. Quantum diffusion Monte Carlo (DMC) and coupled cluster theory with single, double, and perturbative triple excitations [CCSD(T)] are considered two widely trusted methods for treating noncovalent interactions. However, while they have been well-validated for small molecules, recent work has indicated that these two methods can disagree by more than 7.5 kcal/mol for larger systems. The origin of this discrepancy remains unknown. Moreover, the lack of systematic comparisons, particularly for medium-sized complexes, has made it difficult to identify which systems may be prone to such disagreements and the potential scale of these differences. In this work, we leverage the latest developments in DMC to compute interaction energies for the entire S66 dataset, containing 66 medium-sized complexes with a balanced representation of dispersion and electrostatic interactions. Comparison to previous CCSD(T) references reveals systematic trends, with DMC predicting stronger binding than CCSD(T) for electrostatic-dominated systems, while the binding becomes weaker for dispersion-dominated systems. We show that the relative strength of this discrepancy is correlated to the ratio of electrostatic and dispersion interactions, as obtained from energy decomposition analysis methods. Finally, we have pinpointed model systems: the hydrogen-bonded acetic acid dimer (ID 20) and dispersion-dominated uracil-cyclopentane dimer (ID 42), where these discrepancies are particularly prominent. These systems offer cost-effective benchmarks to guide future developments in DMC, CCSD(T), as well as the wider electronic structure theory community.
准确处理非共价相互作用对于模拟从分子晶体到表面催化剂、水溶液等广泛的应用至关重要。量子扩散蒙特卡罗（DMC）和含单、双及微扰三重激发的耦合簇理论[CCSD(T)]被认为是处理非共价相互作用的两种广泛信赖的方法。然而，尽管它们在小分子体系中已得到充分验证，但最近的研究表明，对于更大的体系，这两种方法的计算结果可能相差超过7.5千卡/摩尔。这种差异的根源仍然未知。此外，缺乏系统的比较，特别是对于中等大小的复合物，使得难以确定哪些体系可能容易出现这种差异以及这些差异的潜在规模。在这项工作中，我们利用DMC的最新进展来计算整个S66数据集的相互作用能，该数据集包含66个中等大小的复合物，具有色散和静电相互作用的平衡表示。与先前的CCSD(T)参考文献进行比较揭示了系统趋势，对于以静电为主的体系，DMC预测的结合力比CCSD(T)更强，而对于以色散为主的体系，结合力则较弱。我们表明，这种差异的相对强度与从能量分解分析方法获得的静电和色散相互作用的比率相关。最后，我们确定了模型体系：氢键结合的乙酸二聚体（ID 20）和以色散为主的尿嘧啶 - 环戊烷二聚体（ID 42），在这些体系中这些差异尤为突出。这些体系提供了具有成本效益的基准，以指导DMC、CCSD(T)以及更广泛的电子结构理论领域的未来发展。
