论文标题
变分的局部活动空间自洽场方法
The Variational Localized Active Space Self-Consistent Field Method
论文作者
论文摘要
应用于多方面波函数的碎片化方法构成了将高度准确的Ab in i算波函数计算计算到大分子和固体中的道路。但是，对于可重复性和可传递性很重要，即对初始轨道猜测或用户设计的临时片段化方案的依赖性良好的碎裂方案。改善这种鲁棒性的一种方法是确保能量遵守各种原理。即，活性轨道和活动空间波的功能最小化了某个ANSATZ中的电子能量以用于分子波函数。我们扩展了局部活动空间自洽场的理论，lassCF，方法（JCTC 2019，15，972），以完全最大程度地减少所有轨道旋转的能量，从而使其真正变化。与LASSCF相比，称为vlassCF的新方法显着提高了LAS波函数的鲁棒性和可重复性。我们使用标准CASSCF方法分析了VlassCF的存储和操作成本缩放，并在某些简单的测试系统上显示了VlassCF计算的结果。我们表明，VlassCF在一个有源子空间的极限上等同于CASSCF，并且VlassCF显着提高了LASSCF能量差异的可靠性，从而可以对分离分子的分离分子的势能曲线进行更有意义和细微的分析。我们还表明，所有形式的LASSCF的运行成本缩放比CASSCF的轨道优化部分都低。
Fragmentation methods applied to multireference wave functions constitute a road towards the application of highly accurate ab initio wave function calculations to large molecules and solids. However, it is important for reproducibility and transferability that a fragmentation scheme be well-defined with minimal dependence on initial orbital guesses or user-designed ad hoc fragmentation schemes. One way to improve this sort of robustness is to ensure the energy obeys a variational principle; i.e., that the active orbitals and active space wave functions minimize the electronic energy in a certain ansatz for the molecular wave function. We extended the theory of the localized active space self-consistent field, LASSCF, method (JCTC 2019, 15, 972) to fully minimize the energy with respect to all orbital rotations, rendering it truly variational. The new method, called vLASSCF, substantially improves the robustness and reproducibility of the LAS wave function compared to LASSCF. We analyze the storage and operation cost scaling of vLASSCF compared to orbital optimization using a standard CASSCF approach and we show results of vLASSCF calculations on some simple test systems. We show that vLASSCF is energetically equivalent to CASSCF in the limit of one active subspace, and that vLASSCF significantly improves upon the reliability of LASSCF energy differences, allowing for more meaningful and subtle analysis of potential energy curves of dissociating molecules. We also show that all forms of LASSCF have a lower operation cost scaling than the orbital-optimization part of CASSCF.
