Kreplin David A, Knowles Peter J, Werner Hans-Joachim
Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany.
School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, United Kingdom.
J Chem Phys. 2020 Feb 21;152(7):074102. doi: 10.1063/1.5142241.
A new orbital optimization for the multiconfiguration self-consistent field method is presented. This method combines a second-order (SO) algorithm for the optimization of the active orbitals with the first-order super configuration interaction (SCI) optimization of the remaining closed-virtual rotations and is denoted as the SO-SCI method. The SO-SCI method significantly improves the convergence as compared to the conventional SCI method. In combination with density fitting, the intermediates from the gradient calculation can be reused to evaluate the two-electron integrals required for the active Hessian without introducing a large computational overhead. The orbitals and CI coefficients are optimized alternately, but the CI-orbital coupling is accounted for by the limited memory Broyden-Fletcher-Goldfarb-Shanno quasi-Newton method. This further improves the speed of convergence. The method is applicable to large molecules. The efficiency and robustness of the presented method is demonstrated in benchmark calculations for 21 aromatic molecules as well as for various transition metal complexes with up to 826 electrons and 5154 basis functions.
提出了一种用于多组态自洽场方法的新轨道优化方法。该方法将用于优化活性轨道的二阶（SO）算法与其余闭壳层-虚轨道旋转的一阶超组态相互作用（SCI）优化相结合，被称为SO-SCI方法。与传统的SCI方法相比，SO-SCI方法显著提高了收敛性。结合密度拟合，梯度计算的中间结果可被重新用于评估活性海森矩阵所需的双电子积分，而不会引入大量计算开销。轨道和CI系数交替优化，但CI-轨道耦合由有限内存的布罗伊登-弗莱彻-戈德法布-肖诺拟牛顿法处理。这进一步提高了收敛速度。该方法适用于大分子。在对21个芳香族分子以及具有多达826个电子和5154个基函数的各种过渡金属配合物的基准计算中，证明了所提出方法的效率和稳健性。
