Li Chenyang, Mao Shuxian, Huang Renke, Evangelista Francesco A
Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
Department of Chemistry and Cherry Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, United States.
J Chem Theory Comput. 2024 May 28;20(10):4170-4181. doi: 10.1021/acs.jctc.4c00152. Epub 2024 May 15.
We present a reduced-cost implementation of the state-averaged driven similarity renormalization group (SA-DSRG) based on the frozen natural orbital (FNO) approach. The natural orbitals (NOs) are obtained by diagonalizing the one-body reduced density matrix from SA-DSRG second-order perturbation theory (SA-DSRG-PT2). We consider three criteria to truncate the virtual NOs for the subsequent electron correlation treatment beyond SA-DSRG-PT2. An additive second-order correction is applied to the SA-DSRG Hamiltonian to reintroduce correlation effects from the discarded orbitals. The FNO SA-DSRG method is benchmarked on 35 small organic molecules in the QUEST database. When keeping 98-99% of the cumulative occupation numbers, the mean absolute error in the vertical transition energies due to FNO is less than 0.01 eV. Using the same FNO threshold, we observe a speedup of 9 times compared to the conventional SA-DSRG implementation for nickel carbonyl with a quadruple-ζ basis set. The FNO approach enables nonperturbative SA-DSRG computations on chloroiron corrole [FeCl(CHN)] with more than 1000 basis functions, surpassing the current limit of a conventional implementation.
我们基于冻结自然轨道（FNO）方法提出了一种成本降低的状态平均驱动相似性重整化群（SA-DSRG）实现方案。自然轨道（NOs）通过对SA-DSRG二阶微扰理论（SA-DSRG-PT2）中的一体约化密度矩阵进行对角化得到。我们考虑了三个标准来截断虚拟NOs，以便在SA-DSRG-PT2之外进行后续的电子关联处理。对SA-DSRG哈密顿量应用了一个附加的二阶修正，以重新引入被丢弃轨道的关联效应。FNO SA-DSRG方法在QUEST数据库中的35个小有机分子上进行了基准测试。当保留98 - 99%的累积占据数时，FNO导致的垂直跃迁能量的平均绝对误差小于0.01 eV。使用相同的FNO阈值，与使用四重ζ基组的传统SA-DSRG实现相比，我们观察到对于羰基镍的加速比为9倍。FNO方法能够对具有1000多个基函数的氯铁卟啉[FeCl(CHN)]进行非微扰SA-DSRG计算，超越了传统实现的当前极限。
