Sorathia Kesha, Frantzov Damyan, Tew David P
University of Oxford, South Parks Road, Oxford OX1 3QZ, U.K.
J Chem Theory Comput. 2024 Apr 9;20(7):2740-2750. doi: 10.1021/acs.jctc.3c00974. Epub 2024 Mar 21.
Computation of heats of reaction of large molecules is now feasible using the domain-based pair natural orbital (PNO)-coupled-cluster singles, doubles, and perturbative triples [CCSD(T)] theory. However, to obtain agreement within 1 kcal/mol of experiment, it is necessary to eliminate basis set incompleteness error, which comprises both the AO basis set error and the PNO truncation error. Our investigation into the convergence to the canonical limit of PNO-CCSD(T) energies with the PNO truncation threshold shows that errors follow the model . Therefore, PNO truncation errors can be eliminated using a simple two-point CPS extrapolation to the canonical limit so that subsequent CBS extrapolation is not limited by the residual PNO truncation error. Using the ISOL24 and MOBH35 data sets, we find that PNO truncation errors are larger for molecules with significant static correlation and that it is necessary to use very tight thresholds of to ensure that errors do not exceed 1 kcal/mol. We present a lower-cost extrapolation scheme that uses information from small basis sets to estimate the PNO truncation errors for larger basis sets. In this way, the canonical limit of CCSD(T) calculations on sizable molecules with large basis sets can be reliably estimated in a practical way. Using this approach, we report near complete basis set (CBS)-CCSD(T) reaction energies for the full ISOL24 and MOBH35 data sets.
如今，使用基于域的对自然轨道（PNO）耦合簇单双激发和微扰三激发[CCSD(T)]理论来计算大分子的反应热是可行的。然而，要使计算结果与实验值在1千卡/摩尔范围内相符，就必须消除基组不完备误差，该误差包括原子轨道（AO）基组误差和PNO截断误差。我们对PNO-CCSD(T)能量随PNO截断阈值收敛到正则极限的研究表明，误差符合该模型。因此，可以使用简单的两点CPS外推法将PNO截断误差外推到正则极限，这样后续的完全基组外推（CBS）就不会受到残余PNO截断误差的限制。使用ISOL24和MOBH35数据集，我们发现对于具有显著静态相关的分子，PNO截断误差更大，因此有必要使用非常严格的阈值以确保误差不超过1千卡/摩尔。我们提出了一种低成本的外推方案，该方案利用小基组的信息来估计大基组的PNO截断误差。通过这种方式，可以以实际可行的方式可靠地估计在大基组下对大分子进行CCSD(T)计算的正则极限。使用这种方法，我们报告了完整的ISOL24和MOBH35数据集的近完全基组（CBS）-CCSD(T)反应能量。
