Nonadiabatic Molecular Dynamics and Kinetics with Dynamical Ligand Field

Sergey Varganov of the University of Nevada, Reno is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to develop a novel computational methodology to simulate the behavior of lanthanide-containing molecules after their exposure to light. The Varganov group will implement a very computationally efficient way to describe electron distribution in lanthanide-containing molecules, called a dynamic ligand field (DLF) method. The DLF method will be coupled with nonadiabatic molecular dynamics (NAMD), a state-of-the-art technique to simulate the combined motions of electrons and nuclei in molecules. The resulting NAMD-DLF methodology will be used to model how the energy of absorbed light is distributed between the electrons and nuclei and how the efficiency of spontaneous light emission in lanthanide-containing molecules is affected by molecular vibrations. The ability to accurately predict light emission efficiency is critical in designing new molecules for solar energy conversion, medical imaging, and optical telecommunication. As part of the broader impact, Varganov will use the 3D-printed potential energy surfaces describing nuclei motions in molecules to enhance the quality of instruction in chemistry courses by providing visual demonstrations of complex chemistry concepts. Sergey Varganov will develop a NAMD methodology based on an extremely computationally efficient ab initio DLF theory to simulate nonadiabatic dynamics in lanthanide complexes on an unprecedentedly long time scale. The direct multiple spawning NAMD will be coupled with the DLF method parametrized using ab initio electronic structure calculations. The specific objectives are 1) develop a novel DLF method capable of accounting for both ionic and covalent contributions to metal-ligand bonds at equilibrium and non-equilibrium molecular geometries, 2) implement NAMD-DLF with analytical nonadiabatic coupling and energy gradients, and 3) apply new NAMD-DLF to elucidate complex mechanisms of nonradiative relaxation responsible for luminescence quenching in lanthanide complexes. This project will support the continued use and expansion of the set of 3D-printed potential energy surfaces (PES) to enhance the quality of instruction in chemistry courses and the effectiveness and impact of outreach programs by providing simple visual demonstrations of complex chemistry concepts, such as a transition state, a minimum energy reaction path, and the relation between the PES curvature and vibrational frequencies. The proposed visits of Prof. Chibotaru, a world’s leading expert on electronic structure and properties of lanthanide compounds, will facilitate the professional development and training of graduate students and postdoctoral scholars in Nevada, which is an EPSCoR state. 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.