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Sparse-Stochastic Fragmented Exchange for Large-Scale Hybrid Time-Dependent Density Functional Theory Calculations
Mykola Sereda1, Tucker Allen1, Nadine C Bradbury1
1Department of Chemistry and Biochemistry, and California Nanoscience Institute, UCLA, Los Angeles, California 90095-1569, United States.
Journal of Chemical Theory and Computation
|May 7, 2024
Summary
We developed a new computational method to accurately calculate optical spectra for large molecules using hybrid density functional theory (DFT). This approach efficiently handles thousands of electrons, enabling precise absorption spectrum predictions for complex systems.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Materials Science
Background:
- Accurate calculation of optical spectra is crucial for understanding molecular properties and designing new materials.
- Existing methods for large systems are computationally expensive, limiting their applicability.
- Hybrid Density Functional Theory (DFT) offers a good balance of accuracy and cost but struggles with large system sizes.
Purpose of the Study:
- To develop and present an efficient computational method for calculating absorption spectra of large molecular systems.
- To extend the sparse-stochastic fragmented exchange formalism to linear-response time-dependent generalized Kohn-Sham DFT (LR-GKS-TDDFT).
- To enable accurate optical spectra calculations for systems with thousands of valence electrons.
Main Methods:
- Developed a sparse-stochastic fragmented exchange formalism for ground-state near-gap hybrid DFT.
- Applied this formalism within LR-GKS-TDDFT using a grid-based/plane-wave representation.
- Implemented a mixed deterministic/fragmented-stochastic compression of the exchange kernel using long-range explicit exchange functionals.
- Utilized both real-time propagation and frequency-resolved Casida-equation-type approaches for spectra calculation.
Main Results:
- Successfully calculated accurate optical spectra for large molecular systems, including molecular dyes.
- Demonstrated the efficiency of the mixed deterministic/fragmented-stochastic compression for the exchange kernel.
- The method effectively handles systems with thousands of valence electrons.
Conclusions:
- The developed sparse-stochastic fragmented exchange formalism provides an efficient and accurate method for computing optical spectra in large systems.
- This advancement extends the capabilities of DFT for studying complex molecular materials.
- The approach is applicable to various systems, particularly large molecular dyes, paving the way for future research in computational spectroscopy.
