Oleg Prezhdo - UW Dept. of Chemistry

Professor of Chemistry
Ph.D. University of Texas, Austin, 1997

(Theoretical and Computational Chemistry)

(206) 221-3931

Email: prezhdo@chem.washington.ed u
Prezhdo group website

Research Interests

The research goal of the Prezhdo group is to obtain a theoretical understanding at the molecular level of chemical reactivity and energy transfer in complex condensed-phase chemical and biological environments. This requires the development of new theoretical and computational tools and the application of these tools to challenging chemical problems in direct connection to experiments.

Quantum mechanics, in principle, may be used to describe any chemical process. Its application to systems containing more than a dozen atoms, however, is nearly impossible due to computational constraints. Classical mechanics, on the other hand, may be easily applied to systems of thousands of atoms. Fortunately, in a given chemical system, only a small subset of the particles involved must be treated quantum-mechanically. This has allowed our group to develop a number of mixed quantum-classical approaches that are suitable for different situations. Quantized Hamilton Dynamics, for example, provides a beautiful and remarkably simple extension of classical mechanics that incorporates zero-point motion, tunneling, dephasing and other quantum effects. The Stochastic Mean Field approach deals with chemical reactions involving quantum transitions, such as absorption and emission of light, and conversion of light and electric energy to forming and breaking chemical bonds. Chemical versions of the Schrodinger Cat paradox, the “watched pot never boils”, and quantum Zeno effects are other important phenomena that may be modeled with the Stochastic Mean Field approach. The Bohmian or hydrodynamic interpretation of quantum mechanics is used to couple quantum and classical variables and to interpret results in terms of intuitive particle trajectories. These varied quantum-classical approaches are being implemented within the framework of time-dependent density functional theory.

The Prezhdo group pioneered ab initio real-time simulations of the ultrafast electron injection across the molecule-semiconductor interface that drives Graetzel-type solar cells. Such organic-inorganic interface is critical in molecular electronics and remain the field’s least understood components. The electron-injection mechanism we have established suggests a way to improve the solar cell voltage. Motivated by recent experiments, we have begun modelling electron and hole relaxation dynamics in quantum dots and carbon nanotubes. Impact ionization discovered in PbSe and PbS nanocrystals generates multiple charge carriers per single absorbed photon, indicating the possibility of a highly efficient use of solar power. Simulations of electron-phonon interactions in carbon nanotubes create the theoretical basis for optical and conductance switches, quantum wires, logic gates, miniature field-effect transitions and lasers. The surprising solvent invariance of the OClO relaxation dynamics that is relevant to ozone layer chemistry has been elucidated by quantum-classical molecular dynamics simulations.

In collaboration with colleagues in Microbiology and Bioengineering, our group has begun an investigation of the so-called catch-bond, a fascinating biological phenomenon whereby the application of a pulling force increases bond lifetime (!). A physically intuitive model of the catch-bond has been developed and analyzed, including the derivation of universal laws that unite the experimental data obtained through different pulling regimes. The molecular basis of the catch-bond phenomenon is being elucidated by steered molecular dynamics.

New generations of electro-optic devices based on polymers showing order-disorder transitions are being designed by colleagues in Chemistry and Chemical Engineering. Our group developed a statistical-mechanical model of the ordering that clearly explains how the efficiency of the polymeric materials depends on molecular structure, temperature, electric field and other tunable parameters.

Members of the Prezhdo group use pen-and-paper and computers in their research.