Time propagation of electronic wavefunctions using nonorthogonal determinant expansions

Area of Science:

• Quantum chemistry
• Computational physics
• Electron dynamics simulations

Background:

• Truncated configuration interaction (TCI) offers a computational-accuracy balance for real-time electron dynamics simulations.
• TCI avoids some failures of real-time time-dependent density functional theory (RT-TDDFT).
• Low-order TCI methods can overestimate polarizability, necessitating improved approaches.

Purpose of the Study:

• To investigate the use of nonorthogonality in determinant expansions within TCI.
• To determine if nonorthogonality can recover higher-order substitutions for better electron dynamics description.
• To assess the accuracy of different methods in reproducing (hyper)polarizability and high-harmonic generation spectra.

Main Methods:

• Employing truncated configuration interaction with nonorthogonal determinant expansions.
• Investigating model systems including H2, water, and butadiene.
• Quantifying (hyper)polarizability and high-harmonic generation spectra.

Main Results:

• Nonorthogonality in determinant expansions shows potential for improving electron dynamics simulations.
• The study quantifies the accuracy of TCI with nonorthogonality against established methods.
• Model system results provide insights into the method's performance for specific molecular systems.

Conclusions:

• Nonorthogonal determinant expansions offer a promising avenue for enhancing the accuracy of truncated configuration interaction.
• This approach can lead to improved descriptions of electron dynamics and spectral properties.
• The findings contribute to the development of more reliable computational tools for quantum mechanical systems.