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arXiv · 2409.14631

An Efficient Algorithm for Constrained CASSCF(1,2) and CASSCF(3,2) Simulations as Relevant to Electron and Hole Transfer Problems

Tian Qiu·Joseph E. Subotnik
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Abstract

We propose an efficient algorithm for the recently published electron/hole-transfer Dynamical-weighted State-averaged Constrained CASSCF (eDSC/hDSC) method studying charge transfer states and D$_1$-D$_0$ crossings for systems with odd numbers of electrons. By separating the constrained minimization problem into an unconstrained self-consistent-field (SCF) problem and a constrained non-self-consistent-field (nSCF) problem, and accelerating the direct inversion in the iterative subspace (DIIS) technique to solve the SCF problem, the overall computational cost is reduced by a factor of 8 to 20 compared with directly using sequential quadratic programming (SQP). This approach should be applicable for other constrained minimization problems and, in the immediate future, once gradients are available, the present eDSC/hDSC algorithm should allow for speedy non-adiabatic dynamics simulations.

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Tian Qiu, Joseph E. Subotnik. 2024-09-22. An Efficient Algorithm for Constrained CASSCF(1,2) and CASSCF(3,2) Simulations as Relevant to Electron and Hole Transfer Problems. https://arxiv.org/abs/2409.14631

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