# Xiaosong Li
Xiaosong Li is a theoretical and computational chemist. His research develops time-dependent relativistic and non-relativistic electronic structure theories for excited-state processes that underpin energy conversion, photocatalysis, and ultrafast spectroscopies.[2](https://chem.washington.edu/people/xiaosong-li) He was elected a Fellow of the [American Association for the Advancement of Science](https://www.edgepedia.org/american-association-for-the-advancement-of-science) (AAAS) in 2025 for contributions to time-dependent quantum theory and relativistic electronic structure theory.[3](https://chem.washington.edu/news/2025/03/27/xiaosong-li-elected-aaas-fellow)
| Fact | Detail |
|---|---|
| Current chair | Chair in Chemistry, University of Washington, since 2022[1](https://uwligroup.org/wp-content/uploads/2026/04/Li-CV-2026.3.29.pdf) |
| Signature method | Real-time TDDFT, including a relativistic two-component implementation (2016)[4](https://pubs.acs.org/doi/full/10.1021/acs.chemrev.0c00223) |
| 2025 landmark | Numerically exact configuration interaction at quadrillion-determinant scale, Nature Communications[5](https://www.nature.com/articles/s41467-025-65967-7.pdf) |
| Signature work | ["On the Physical Origin of Blue-Shifted Hydrogen Bonds"](https://doi.org/10.1021/ja020213j), *Journal of the American Chemical Society*, 2002 |
## Career and appointments
Li joined the University of Washington as an Assistant Professor of Chemistry in the fall of 2005.[2](https://chem.washington.edu/people/xiaosong-li) Since 2020 he has held a dual appointment as Lab Fellow at [Pacific Northwest National Laboratory](https://www.edgepedia.org/pacific-northwest-national-laboratory), and he directs the Early Career Network of the IDREAM Energy Frontier Research Center.[1](https://uwligroup.org/wp-content/uploads/2026/04/Li-CV-2026.3.29.pdf) • [7](https://uwligroup.org/people/xiaosong-li/)
## Representative work
**Real-time electronic structure.** Li works on real-time time-dependent electronic structure theory, in which the quantum equations for the electrons are propagated directly in time rather than through perturbative response functions. A review in *Chemical Reviews* describes these methods as providing an unprecedented view of electron dynamics and ultrafast spectroscopy on the atto- and femtosecond time scale.[4](https://pubs.acs.org/doi/full/10.1021/acs.chemrev.0c00223) In 2014, Li and coworkers introduced a nonrelativistic real-time time-dependent two-component method to simulate electron spin dynamics, showing that ab initio simulation of spin dynamics requires at least two components in the electronic description.[4](https://pubs.acs.org/doi/full/10.1021/acs.chemrev.0c00223) According to a review in *Chemical Reviews*, after the first fully relativistic four-component real-time TDDFT appeared in 2015, Li introduced a formally equivalent relativistic two-component implementation (2c-RT-TDDFT) in 2016, enabling computational study of magnetic and spin-orbit effects in spectroscopy and electronic dynamics.[4](https://pubs.acs.org/doi/full/10.1021/acs.chemrev.0c00223)
**Solvated electron and charge-transfer dynamics.** A 2012 paper in the *Journal of Physical Chemistry A* coupled solvent electronic degrees of freedom to the time-dependent electronic density of a solute through the implicit reaction field, propagating the entire electronic system in time; the approach was shown to be very effective in describing dynamical solvation effects in charge-transfer processes.[8](https://doi.org/10.1021/jp2123899) A companion 2012 paper in the *Journal of Physical Chemistry Letters* added a solvent relaxation mechanism, modeled by a time-dependent dielectric relaxation function, and yielded results consistent with experimental observations.[9](https://doi.org/10.1021/jz301042f)
**Quadrillion-determinant configuration interaction.** A 2025 *Nature Communications* paper with Li as corresponding author reports a numerically exact configuration interaction calculation at quadrillion-determinant scale. Compared with previous state-of-the-art CI calculations, the work achieves a 1000-fold increase in CI space, a 106-fold increase in floating-point operations performed, and a 106-fold improvement in memory and computational cost.[5](https://www.nature.com/articles/s41467-025-65967-7.pdf)
## Software and methods
Li's group develops ChronusQ, an open-source quantum chemistry platform integrating advanced relativistic methods and real-time electronic structure theories at scale.[1](https://uwligroup.org/wp-content/uploads/2026/04/Li-CV-2026.3.29.pdf) His contributions to the commercial Gaussian package include ab initio direct dynamics, time-dependent electronic structure theory, low-scaling excited-state methods, energy-specific linear response TDDFT, second derivatives of excited states, and linear scaling SCF, as well as the time-dependent polarizable continuum model, nonadiabatic electronic dynamics with Ehrenfest molecular dynamics, and relativistic many-body theories.[6](http://www.gaussian.com/x_li/) The group's stated focus is on non-adiabatic reactions in large systems such as polymers, biomolecules, and clusters.[10](https://www.cei.washington.edu/people/xiaosong-li/) Current research directions include relativistic electronic structure with two- and four-component Dirac–Coulomb–Breit Hamiltonians for rare-earth and heavy elements, real-time many-body electron dynamics, Nuclear-Electronic Orbital (NEO) theory, and AI-driven error mitigation for variational quantum eigensolvers.[1](https://uwligroup.org/wp-content/uploads/2026/04/Li-CV-2026.3.29.pdf)
## Honors and recognition
The AAAS election, announced March 27, 2025, cited his contributions to the development and application of time-dependent quantum theory and relativistic electronic structure theory, and his work advancing educational pathways and diversity in STEM.[3](https://chem.washington.edu/news/2025/03/27/xiaosong-li-elected-aaas-fellow)
## Recent developments
Since 2023, Li's record has expanded on several fronts. On the research side, the 2025 *Nature Communications* quadrillion-determinant CI result pushed numerically exact electronic structure to a scale a thousand times larger in CI space than prior state-of-the-art work.[5](https://www.nature.com/articles/s41467-025-65967-7.pdf)
## References
1. Xiaosong Li, Curriculum Vitae (updated March 29, 2026). https://uwligroup.org/wp-content/uploads/2026/04/Li-CV-2026.3.29.pdf
2. Xiaosong Li, UW Department of Chemistry faculty page. https://chem.washington.edu/people/xiaosong-li
3. Xiaosong Li elected AAAS Fellow, UW Chemistry news, March 27, 2025. https://chem.washington.edu/news/2025/03/27/xiaosong-li-elected-aaas-fellow
4. Real-Time Time-Dependent Electronic Structure Theory. *Chemical Reviews*. https://pubs.acs.org/doi/full/10.1021/acs.chemrev.0c00223
5. Numerically exact configuration interaction at quadrillion-determinant scale. *Nature Communications*, 2025. https://www.nature.com/articles/s41467-025-65967-7.pdf
6. Xiaosong Li, Gaussian.com. http://www.gaussian.com/x_li/
7. Xiaosong Li, Li group website (people page). https://uwligroup.org/people/xiaosong-li/
8. Modeling Ultrafast Solvated Electronic Dynamics Using TDDFT and Polarizable Continuum Model. *J. Phys. Chem. A*, 2012. https://doi.org/10.1021/jp2123899
9. Solvated First-Principles Excited-State Charge-Transfer Dynamics with Time-Dependent Polarizable Continuum Model. *J. Phys. Chem. Lett.*, 2012. https://doi.org/10.1021/jz301042f
10. Xiaosong Li, Clean Energy Institute, University of Washington. https://www.cei.washington.edu/people/xiaosong-li/
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*Topic: Encyclopedia › Physical world and mathematics › Physical and mathematical scientists › Chemists › Researchers in physical, theoretical, and computational chemistry › Spectroscopy theory and ultrafast/attosecond dynamics*
*Initially written Sep 21, 2026 · Reviewed: Sep 25, 2026 · Edited: Sep 25, 2026; Oct 15, 2026; Oct 21, 2026 · Last review: Sep 25, 2026*
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