Quantum Dynamics with Nuclear Quantum Effects: a Hhierarchical Methodology for Large Molecular Systems

With support from the Chemical Theory, Models and Computational Methods (CTMC) program in the Division of Chemistry, and the Established Program to Stimulate Competitive Research (EPSCoR), Professor Sophya Garashchuk of the University of South Carolina will develop theoretical and computational methods incorporating the quantum behavior of the nuclei within molecules and materials. This research aims to gain in-depth understanding of the properties of molecular assemblies and nanomaterials and their interactions with light, electric current and heat through the first-principles modeling and theoretical analysis, spanning several orders of magnitude in time and space.

The developed methodology will be applied to experimental systems, helping to elucidate the intrinsic mechanisms of chemical reactivity and charge and energy transfer, and to predict the rates of such processes. Modeling system properties and responses to external stimuli, such as temperature, electric and magnetic fields, will guide experiment, accelerating the development of new materials and molecular devices for wide-range applications from fuel cells to catalysis, to quantum technologies.

Professor Garashchuk's research and educational activities will contribute to the development of the emerging quantum information science and technology work force. She will actively promote computational chemistry tools in education and research among students and scientists at her university and at predominantly undergraduate institutions in the state of South Carolina.

Her research group will participate in K-12 science demonstrations and science showcases highlighting the role of chemistry in the forefront scientific advances and in everyday technologies. These activities will broaden participation of the underrepresented groups in research and communicate STEM (science, technology, engineering and mathematics) achievements to the general public of South Carolina, a state geographically underrepresented in the global research enterprise.

The theoretical framework being developed under this award will include a quantum mechanical description of light nuclei, such as protons, ubiquitous in aqueous solutions and biological and nanodevice environments. Because of the exponential scaling of the numerical cost, this rigorous treatment is feasible for just a few nuclei, and it will be reserved for the chemically active light nuclei.

This level of description will be merged with the classical representations of the larger molecular environment affecting the energy and charge flow due to small amplitude nuclear motion and structural rearrangements. This hierarchical approach will be based on the time-dependent Gaussian bases tailored to an evolving wavefunction for the fully quantum nuclei, integrated with a simplified quantum (e. g. thawed Gaussian) description of the heavy nuclei, compatible with on-the-fly electronic structure evaluation, and will be extended to electronically nonadiabatic processes.

Garashchuk will also develop nuclear-subspace factorized electron-nuclear dynamics based on probability density continuity. This formalism will be used to target molecular dynamics involving a large number of electronic states coupled through nuclear motion and external fields, e.g. molecule/nanoparticle systems. In the area of education and broader impacts, Garashchuk will train junior researchers in theoretical, computational chemistry, and high-performance computing; she will facilitate use of computational chemistry tools by experimental colleagues through formal teaching and collaborative projects.

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.