Ma Qianli, Schwilk Max, Köppl Christoph, Werner Hans-Joachim
Institut für Theoretische Chemie, Universität Stuttgart , Pfaffenwaldring 55, D-70569 Stuttgart, Germany.
J Chem Theory Comput. 2017 Oct 10;13(10):4871-4896. doi: 10.1021/acs.jctc.7b00799. Epub 2017 Sep 28.
We present an efficient explicitly correlated pair natural orbital local coupled cluster (PNO-LCCSD-F12) method. The method is an extension of our previously reported PNO-LCCSD approach ( Schwilk et al., J. Chem. Theory Comput. 2017 , 13 , 3650 - 3675 ). Near linear scaling with the molecular size is achieved by using pair, domain, and projection approximations, local density fitting and local resolution of the identity, and by exploiting the sparsity of the local molecular orbitals as well as of the projected atomic orbitals. The effect of the various domain approximations is tested for a wide range of chemical reactions and intermolecular interactions. In accordance with previous findings, it is demonstrated that the F12 terms significantly reduce the domain errors. The convergence of the reaction and interaction energies with respect to the parameters that determine the domain sizes and pair approximations is extensively tested. The results obtained with our default thresholds agree within a few tenths of a kcal mol with the ones computed with very tight options. For cases where canonical calculations are still feasible, the relative energies of local and canonical calculations agree within similar error bounds. The PNO-LCCSD-F12 method needs only 25-40% more computer time than a corresponding PNO-LCCSD calculation while greatly improving the accuracy. Our program is well parallelized and capable of computing accurate correlation energies for molecules with more than 150 atoms using augmented triple-ζ basis sets and more than 5000 basis functions. Using several nodes of a small computer cluster, such calculations can be carried out within a few hours.
我们提出了一种高效的显式相关对自然轨道局部耦合簇（PNO-LCCSD-F12）方法。该方法是我们之前报道的PNO-LCCSD方法（施维尔克等人，《化学理论与计算杂志》，2017年，13卷，3650 - 3675页）的扩展。通过使用对、域和投影近似、局部密度拟合和单位分解的局部化，以及利用局部分子轨道和投影原子轨道的稀疏性，实现了与分子大小近乎线性的缩放比例。针对广泛的化学反应和分子间相互作用，测试了各种域近似的效果。与之前的研究结果一致，证明F12项显著降低了域误差。广泛测试了反应和相互作用能相对于决定域大小和对近似的参数的收敛性。使用我们的默认阈值得到的结果与使用非常严格选项计算的结果在几十分之一千卡每摩尔的范围内一致。对于规范计算仍然可行的情况，局部计算和规范计算的相对能量在类似的误差范围内一致。PNO-LCCSD-F12方法只比相应的PNO-LCCSD计算多需要25% - 40%的计算机时间，同时大大提高了精度。我们的程序具有良好的并行性，能够使用增强的三重ζ基组和超过5000个基函数为具有150多个原子的分子计算精确的相关能。使用小型计算机集群的几个节点，这样的计算可以在几个小时内完成。
