Ab Initio Methods for Simulating Time-Resolved Magnetic Circular Dichroism

Xiaosong Li of the University of Washington is supported by the Chemical Theory, Models, and Computational Methods program in the Division of Chemistry to develop advanced computational methods for understanding quantum phenomena driven by magnetic fields. These magnetic-field-induced processes are fundamental to breakthroughs in chemical transformations, quantum materials, and quantum information science, with broad applications that can benefit society. Xiaosong Li will simulate microscopic quantum dynamics on experimentally relevant time scales, enabling deeper insight into how magnetic fields control molecular and electronic behavior. The new methods will provide a foundation for the rational design of next-generation quantum technologies and energy-efficient materials. In addition to advancing scientific knowledge, this research supports interdisciplinary education and training at the interface of inorganic, physical, theoretical, and materials chemistry. Undergraduate and graduate students involved in the project will gain hands-on experience in computational science and high-performance software development, equipping them with essential skills for careers in science, engineering, and education. Xiaosong Li will establish a rigorous first-principles framework for modeling time-resolved magnetic circular dichroism (MCD) spectroscopy. At its core is the development of a relativistic, time-dependent multiconfigurational approach capable of simulating MCD spectral evolution on attosecond to femtosecond timescales under finite magnetic fields. Complementary nuclear gradient techniques will be implemented to enable geometry optimization and excited-state characterization within relativistic multireference calculations. Together, these methods will allow for the simulation and interpretation of femtosecond-to-picosecond time-resolved MCD spectra, facilitating detailed structural and electronic analysis of complex molecular systems. A central application of this framework will focus on elucidating the covalency and electronic structure of rare-earth-doped magnetic complexes by tracking their evolving MCD signatures. These advances will offer new insights into excited-state dynamics and catalytic processes that are critical to chemical reactivity, energy conversion, and quantum materials design. All computational methods developed through this work will be integrated into Chronus Quantum, an open-source software platform. Broad dissemination of these capabilities will provide the scientific community with advanced tools for simulating magnetic and time-resolved spectroscopies, promoting reproducibility, enabling interdisciplinary collaboration, supporting education and training, and accelerating discovery in quantum chemistry, materials science, and condensed matter physics. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.