Non-adiabatic quantum molecular dynamics of complex systems

• Applicant: Dr. Ralph Welsch
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: from 2014 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 268264102

• Final Report Year: 2017

Final Report Abstract

In summary, during my postdoctoral scholarship I conducted research in three very different areas of physical chemistry, which all showed some interesting and important progress as well as valuable results published in high-level, peer-reviewed journals. Specifically, I showed that RPMD and CMD can be efficiently employed to study the quantum dynamics of systems associated with non-equilibrium initial conditions, how minute changes in hydrogen bonding networks can lead to surprising effects on ESIPT, and that the newly developed 2D-TTR spectroscopy is a valuable and versatile tool to investigate non-linearities and anharmonicities in liquid systems. On a more personal note, I familiarized myself with various new simulation methodologies like path-integral based methods, molecular dynamics approaches, excited-state electronic structure calculations, semi-classical transition state theory and polarizable continuum models. Furthermore, I got significant insight into various different areas of physical chemistry like non-equilibrium dynamics, condensedphase reactions, excited-state dynamics, several different forms of spectroscopy, like pump-probe spectroscopy, two-dimensional spectroscopy, and, Terahertz spectroscopy, as well as experience with multiple program packages (e.,g., Gaussian, Molpro, GROMACS, LAMMPS). Last, but not least, I gained a lot of experience in starting and maintaining collaborations with experimental and theoretical scientists. Thus, while I could not achieve all the goals set out in my original proposal, I think this post-doctoral work prepared me very well for a future career in academia.

Publications

• “Coherent two-dimensional terahertz-terahertz-raman spectroscopy”, Proc. Natl. Acad. Sci. USA 113, 6857 (2016)
  I. A. Finneran, R. Welsch, M. A. Allodi, T. F. Miller, and G. A. Blake
  (See online at https://doi.org/10.1073/pnas.1605631113)
• “Molecular seesaw: How increased hydrogen bonding can hinder excited-state proton transfer”, J. Phys. Chem. Lett. 7, 3616 (2016)
  R. Welsch, E. Driscoll, J. M. Dawlaty, and T. F. Miller III
  (See online at https://doi.org/10.1021/acs.jpclett.6b01391)
• “Nonequilibrium quantum correlation functions from RPMD and CMD”, J. Chem. Phys. 145, 204118 (2016)
  R. Welsch, K. Song, Q. Shi, S. C. Althorpe, and T. F. Miller III
  (See online at https://doi.org/10.1063/1.4967958)