Chemistry at Illinois University of Illinois at Urbana-Champaign

Nancy Makri

Gutgsell Professor
Professor of Chemistry
Professor of Physics

Professor Nancy Makri received her B.S. from the University of Athens in 1985 and her Ph.D. from the University of California at Berkeley in 1989. She spent two years as a Junior Fellow at Harvard before joining the faculty at Illinois in the spring of 1992. Her research interests are in theoretical quantum dynamics.

Research

We strive to advance theoretical understanding of quantum mechanical processes in large molecules and the condensed phase. Full solution of the Schrödinger equation is feasible only for small molecules, as the required numerical effort increases exponentially with the number of particles. We develop new theoretical approaches and simulation methods based on Feynman’s path integral formulation of quantum dynamics and its semiclassical limit.

Methodology. The path integral representation avoids storage of multidimensional wave functions at the cost of introducing auxiliary integration variables at each time step. Evaluating the resulting multidimensional integrals presents a challenge: the number of paths grows exponentially with time, while importance sampling fails due to phase cancellation.

We developed the first rigorous methodology for following the dynamics of a quantum particle interacting with a polyatomic medium. A path integral represents the subsystem of interest, while the collective effects of the environment are evaluated in the semiclassical approximation using trajectories in combined forward-backward time to alleviate the phase cancellation problem. Through dephasing effects, the medium helps shorten the range of temporal correlations, allowing an exact decomposition of the path sum into an iterative scheme that circumvents the need for global summation over astronomical numbers of paths. The method allows a faithful description of all aspects of quantum mechanical processes in condensed phase environments and, if the environment consists of harmonic phonon modes, yields the exact quantum mechanical result.

Reaction Rates. We have performed path integral calculations to benchmark adiabatic and nonadiabatic reaction rates in generic dissipative environments and to explore the interplay between coherence and dissipation at low temperatures. Our simulation of hydrogen diffusion in silicon identified important tunneling contributions and an inverse isotope effect.

Photosynthesis. Our path integral simulations helped resolve a long-standing controversy concerning the primary charge separation mechanism. Further, we have been exploring the energy transfer process in light-harvesting complexes using the path integral representation of quantum statistical mechanics.

Quantum Control. We are investigating the possibility of using coherent light to manipulate exciton tunneling and transport in nanostructures. We have identified novel mechanisms for sustaining charge localization or inducing coherent oscillations in semiconductor double-quantum wells.

Publications

E. Bukhman and N. Makri, "Forward-backward semiclassical dynamics with information-guided noise reduction for a molecule in solution", J. Phys. Chem. A 111, 11320-11327 (2007).

N. Makri, "Equilibrium and dynamical path integral methods in bacterial photosynthesis", in Biophysical Techniques in Photosynthesis, Volume II (Thijs J. Aartsma and Jörg Matysik, eds.), Series Advances in Photosynthesis and Respiration, Vol. 26, Springer, Dordrecht (2008).

J. Chen and N. Makri, "Forward-backward semiclassical dynamics with single-bead coherent state density", Mol. Phys. 106, 443-453 (2008).

J. Kegerreis, A. Nakayama and N. Makri, "Complex-time velocity autocorrelation functions for Lennard-Jones fluids with quantum pair-product propagators", J. Chem. Phys. 128, 184509 (2008).

V. Jadhao and N. Makri, "Iterative Monte Carlo for quantum dynamics", J. Chem. Phys. Communication (submitted).

Awards

  • Fellow, American Physical Society, 2001
  • Bodossaki Academic Prize in Physical Sciences, 2000
  • University Scholar, 1999
  • Agnes Fay Morgan Research Award, 1999
  • Fellow, American Association for the Advancement of Science, 1998
  • Camille Dreyfus Teacher Scholar Award, 1997
  • Annual Medal of the International Academy of Quantum Molecular Science, 1995
  • Cottrell Scholar Award, 1994
  • Sloan Research Fellowship, 1994
  • Packard Fellowship for Science and Engineering, 1993
  • National Science Foundation Young Investigator Award, 1993
  • Beckman Young Investigator Award, 1993

    Highlights

    Patents

    Photo of Nancy Makri