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
  
• “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
  
• “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