Self-Consistent Constricted Variational Theory RSCF-CV(∞)-DFT and Its Restrictions To Obtain a Numerically Stable...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Accurate calculation of triplet excitation energies is crucial in various chemical applications.
• Existing methods may face challenges in computational efficiency and numerical stability.

Purpose of the Study:

• To present and validate a new computational approach, RSCF-CV(∞)-DFT, for triplet calculations.
• To introduce and assess numerically stable ΔSCF-DFT-like methods derived from RSCF-CV(∞)-DFT.

Main Methods:

• Implementation of optimized transition matrix for vertical triplet excitations within RSCF-CV(∞)-DFT.
• Development of restricted RSCF-CV(∞)-DFT methods, including SVD-RSCF-CV(∞)-DFT.
• Validation using a benchmark test set and comparison with ΔSCF-DFT.

Main Results:

• The RSCF-CV(∞)-DFT approach provides reliable excitation energies.
• SVD-RSCF-CV(∞)-DFT closely mimics the performance of ΔSCF-DFT.
• Root-mean-square deviations between SVD-RSCF-CV(∞)-DFT and ΔSCF-DFT are below 0.1 eV.

Conclusions:

• The presented RSCF-CV(∞)-DFT method and its implementation are validated for triplet calculations.
• Numerically stable ΔSCF-DFT-like methods based on RSCF-CV(∞)-DFT are effective.
• The findings offer a reliable and accurate computational tool for studying triplet states.