Department of Mathematics, Duke University, Durham, North Carolina 27708, United States.
Department of Chemistry and Department of Physics, Duke University, Durham, North Carolina 27708, United States.
J Chem Theory Comput. 2020 Oct 13;16(10):6207-6221. doi: 10.1021/acs.jctc.0c00613. Epub 2020 Aug 28.
Full configuration interaction (FCI) solvers are limited to small basis sets due to their expensive computational costs. An optimal orbital selection for FCI (OptOrbFCI) is proposed to boost the power of existing FCI solvers to pursue the basis set limit under a computational budget. The optimization problem coincides with that of the complete active space SCF method (CASSCF), while OptOrbFCI is algorithmically quite different. OptOrbFCI effectively finds an optimal rotation matrix via solving a constrained optimization problem directly to compress the orbitals of large basis sets to one with a manageable size, conducts FCI calculations only on rotated orbital sets, and produces a variational ground-state energy and its wave function. Coupled with coordinate descent full configuration interaction (CDFCI), we demonstrate the efficiency and accuracy of the method on the carbon dimer and nitrogen dimer under basis sets up to cc-pV5Z. We also benchmark the binding curve of the nitrogen dimer under the cc-pVQZ basis set with 28 selected orbitals, which provide consistently lower ground-state energies than the FCI results under the cc-pVDZ basis set. The dissociation energy in this case is found to be of higher accuracy.
由于计算成本高昂，全组态相互作用（FCI）求解器的基组规模受到限制。本文提出了一种用于 FCI 的最优轨道选择（OptOrbFCI）方法，旨在利用现有的 FCI 求解器，在计算预算内逼近基组极限，提升其能力。该优化问题与完全活性空间自洽场方法（CASSCF）相同，但其算法完全不同。OptOrbFCI 通过直接求解约束优化问题，有效地找到最优旋转矩阵，将大基组的轨道压缩到可管理大小的轨道集上，仅在旋转轨道集上进行 FCI 计算，并生成变分基态能量及其波函数。本文结合坐标下降全组态相互作用（CDFCI）方法，在高达 cc-pV5Z 的基组上对碳二聚体和氮二聚体进行了基准测试，证明了该方法的效率和准确性。本文还在 28 个选定轨道的 cc-pVQZ 基组下，对氮二聚体的结合曲线进行了基准测试，结果表明，该方法的基态能量始终低于 cc-pVDZ 基组下的 FCI 结果。在这种情况下，解离能的精度更高。
