Faculty Research
Alphabetical · By research area

Our research encompasses a wide variety of problems, but a common thread connects them: partitioning an overall system into a subsystem of interest and its environment, and then exploring the influence of the environment on the dynamics and spectroscopy of the subsystem. We take a mixed quantum-classical approach to modeling, in which the subsystem is treated quantum mechanically while the dynamics of the environment is described by classical mechanics. Our interests lie in the development of mixed quantum-classical methodologies and their application to the spectroscopy of chemical and biological problems of fundamental and technological importance.

The research program can be divided into two areas:

1. Mixed quantum-classical formulation of nonlinear spectroscopy

(a) Simulating the quantum dynamics of processes occurring in classical condensed phase hosts

Starting from the mixed quantum-classical Liouville (MQCL) equation of motion, it is possible to construct practical trajectory-based algorithms for simulating the dynamics of a quantum subsystem coupled to a classical environment. Over the past few years, several methods have been successfully applied in the treatment of simple model systems, but their implementation has been less straightforward in the case of more complex systems. It is our desire to develop and implement schemes based on the MQCL equation, which overcome the pitfalls of existing algorithms when dealing with complex, many-body systems.

(b) Modeling of multidimensional nonlinear spectra

Ultrafast nonlinear spectroscopy is capable of probing molecular dynamics on the femtosecond time scale. Often the resulting spectra are complex, thereby requiring a theoretical framework for their interpretation. Moreover, with comparisons between simulated and experimentally measured spectra becoming increasingly sophisticated, the development and implementation of accurate methods for modeling spectroscopic response is timely. The MQCL approach provides a convenient way for simulating laser-driven dynamics and will thus provide a suitable platform for the development of a general framework for calculating multidimensional nonlinear spectra.

2. Applications to the multidimensional infrared spectroscopy of chemical and biological systems in nanoconfined environments

We are interested in simulating two-dimensional infrared (2DIR) spectra to study the structure and dynamics of a wide variety of nanoconfined systems of experimental interest, some examples of which include:

(a) Nanoconfined water

In many chemical and biological systems, water molecules can be confined on nanometer length scales. Under these circumstances, the molecules are in contact with different types of interfaces. Near an interface, the hydrogen bonding network of water changes considerably because it must adjust to the shape of that interface. As a result, the properties and dynamics of nanoconfined water differ substantially from those of bulk water and must therefore be studied independently.

(b) Nanoconfined nonaqueous polar liquid clusters

Proton transfer in nanoconfined nonaqueous polar liquid clusters represents a class of reactions that are ubiquitous in chemistry. This charge transfer reaction is strongly coupled to the polar solvent and will therefore be greatly affected by solvent confinement. For example, several experiments have shown that the proton transfer rate constant can decrease significantly upon confinement. As a result of this sensitivity, one may design materials with specific chemical purposes by simply varying properties of the cluster such as its size and shape.

(c) Hydrogen transfer in enzymatic catalysis

Hydrogen transfer reactions are ubiquitous in enzymatic catalysis. The interior of an enzyme can create a nanoconfined environment around its active site and this confinement may play an important role in its function. Studying the effects of factors such as hydrogen tunneling and enzymatic motions is crucial for a detailed understanding of the transfer mechanism.

Our group is currently seeking researchers at all levels (postdoctoral, graduate, and undergraduate). In particular, those with interests and/or a solid background in quantum mechanics, statistical mechanics, and applied mathematics are encouraged to apply. Please feel free to contact me for more information on any of the positions or projects.

Selected Publications

Hanna, G.; Geva, E. “Multi-dimensional spectra via the mixed quantum-classical Liouville method: Signatures of nonequilibrium dynamics” Journal of Physical Chemistry B, 2009, 113: 9278-9288.

McRobbie, P.; Hanna, G.; Shi Q.; Geva, E. “Signatures of nonequilibrium solvation dynamics on multi-dimensional spectra” Accounts of Chemical Research, 2009, Articles ASAP.

Hanna, G.; Geva, E. “Isotope effects on the vibrational relaxation and multidimensional infrared spectra of the hydrogen-stretch in a hydrogen-bonded complex dissolved in a polar liquid” Journal of Physical Chemistry B, 2008, 112: 15793-15800.

Hanna, G.; Geva, E. “Computational study of the one and two dimensional infrared spectra of a vibrational mode strongly coupled to its environment: Beyond the cumulant and Condon approximations” Journal of Physical Chemistry B, 2008, 112: 12991-13004.

Hanna, G.; Geva, E. “Vibrational energy relaxation of a hydrogen-bonded complex dissolved in a polar liquid via the mixed quantum-classical Liouville method” Journal of Physical Chemistry B, 2008, 112: 4048-4058.

Hanna, G.; Kapral, R. “Quantum-classical Liouville dynamics of proton and deuteron transfer rates in a solvated hydrogen-bonded complex” Journal of Chemical Physics, 2008, 128: 164520(1)-164520(9).

Kim H.; Hanna, G.; Kapral, R. “Analysis of kinetic isotope effects for nonadiabatic reactions” Journal of Chemical Physics, 2006, 125: 084509(1)-084509(8).

Hanna, G.; Kim, H.; Kapral, R. “Quantum-classical reaction rate theory” In Quantum Dynamics of Complex Molecular Systems, edited by D. Micha and I. Burghardt (Springer-Verlag, Paris), 2006, 281-305.

Hanna, G.; Kapral, R. “Nonadiabatic dynamics of condensed phase rate processes” Accounts of Chemical Research, 2006, 39: 21-27.

Hanna, G.; Kapral, R. “Quantum-classical Liouville dynamics of nonadiabatic proton transfer” Journal of Chemical Physics, 2005, 122: 244505(1)-244505(11).