Theoretical and computational chemical physics
Computing charge migration with TDDFT
When forced out of equilibrium, electrons in matter react exceedingly fast, on time scales approaching the attosecond. Driven by electron correlation, these coherent ultrafast dynamics are called charge migration and are currently an active field of research in ultrafast science. The theoretical study of molecular charge migration, however, is a formidable endeavor as it necessitates models with multiple interacting electrons. Here we investigate charge migration in organic molecules using time-dependent density-functional theory (TDDFT) and develop an attochemistry picture of the dynamics, e.g., with describing the migration through an electron-pushing mechanism inspired from organic chemistry.
Picture from: The Journal of Physical Chemistry Letters 8, 3991 (2017)
A.S. Folorunso, F. Mauger, K.A. Hamer, D.D. Jayasinghe, I.S. Wahyutama, J.R. Ragains, R.R. Jones, L.F. DiMauro, M.B. Gaarde, K.J. Schafer, and K. Lopata, "Attochemistry Regulation of Charge Migration," Journal of Physical Chemistry A 127, 1894 (2023).
F. Mauger, A.S. Folorunso, K.A. Hamer, C. Chandre, M.B. Gaarde, K. Lopata, and K.J. Schafer, "Charge migration and attosecond solitons in conjugated organic molecules," Physical Review Research 4, 013073 (2022).
A.S. Folorunso, A. Bruner, F. Mauger, K.A. Hamer, S. Hernandez, R.R. Jones, L.F. DiMauro, M.B. Gaarde, K.J. Schafer, and K. Lopata, "Molecular Modes of Attosecond Charge Migration," Physical Review Letters 126, 133002 (2021).
A. Bruner, S. Hernandez, F. Mauger, P.M. Abanador, D.J. LaMaster, M.B. Gaarde, K.J. Schafer, and K. Lopata, "Attosecond Charge Migration with TDDFT: Accurate Dynamics from a Well-Defined Initial State," The Journal of Physical Chemistry Letters 8, 3991 (2017).
Simulating strong-field science with TDDFT
Strong-field science, which studies the interaction between very strong (and short) laser pulses and matter, has emerged as one of the leading means to manipulate and probe electronic structures at the scales of atoms and molecules. For complex molecules, with multiple correlated electrons, numerical simulations of those strong-laser-matter interactions are a formidable task. Here we report results using time-dependent density-functional theory (TDDFT) and show qualitative/quantitative agreement when compared with experimental results and other simulations.
Picture from: The Journal of Chemical Physics 151, 194308 (2019)
P Sándor, A. Sissay, F. Mauger, M.W. Gordon, T.T. Gorman, T.D. Scarborough, M.B. Gaarde, K. Lopata, K.J. Schafer, and R.R. Jones, "Angle-dependent strong-field ionization of halomethanes," The Journal of Chemical Physics 151, 194308 (2019).
F. Mauger, P.M. Abanador, T.D. Scarborough, T.T. Gorman, P. Agostini, L.F. DiMauro, K. Lopata, K.J. Schafer, and M.B. Gaarde, "High-harmonic spectroscopy of transient two-center interference calculated with time-dependent density-functional theory," Structural Dynamics 6, 044101 (2019).
T.T. Gorman, T.D. Scarborough, P.M. Abanador, F. Mauger, D. Kiesewetter, P. Sándor, S. Khatri, K. Lopata, K.J. Schafer, P. Agostini, M.B. Gaarde, and L.F. DiMauro, "Probing the interplay between geometric and electronic-structure features via high-harmonic spectroscopy," The Journal of Chemical Physics 150, 184308 (2019).
P. Sándor, A. Sissay, F. Mauger, P.M. Abanador, T.T. Gorman, T.D. Scarborough, M.B. Gaarde, K. Lopata, K.J. Schafer, and R.R. Jones, "Angle dependence of strong-field single and double ionization of carbonyl sulfide," Physical Review A 98, 043425 (2018).
A. Sissay, P. Abanador, F. Mauger, M. Gaarde, K.J. Schafer, and K. Lopata, "Angle-dependent strong-field molecular ionization rates with tuned range-separated time-dependent density functional theory," The Journal of Chemical Physics 145, 094105 (2016).