Styliani Constas
Associate Professor
B.Sc. (University of Athens, Greece)
M.Sc. (Queen's University, Kingston, Canada)
Ph.D. (University of Toronto)
Marie Curie Fellow (AMOLF, Amsterdam, The Netherlands)
Office: Room 071, Lab Room 068, Chemistry Building
(519) 661-2111 ext. 86338
Theoretical physical chemistry; Computer simulations in Condensed Phase
Awards:
• Accelerator Grant for Exceptional New Opportunities (AGENO), NSERC
Current Research Programs:
We study dynamics of activated processes such as chemical
reactions in solution, conformational changes of macromolecules and
disintegration mechanisms of charged nanodroplets. The studies are
performed by molecular simulations where we focus on development and
application of Molecular Dynamics and Monte Carlo techniques. Sizes of
systems that are investigated range from clusters to bulk. The systems
are modeled on atomic scale using different levels of description that
range from quantum chemical to empirical in order to capture features
defining the properties of the systems.
Charged nanodroplets and clusters
Charged droplets are ubiquitous in atmospheric aerosols and experimental
techniques such as electrospray mass spectrometry. We study the
mechanism and dynamics of disintegration of the charged nanodroplets
with respect to volume to charge ratio. We also study proton transfer
reactions in the unique environment of the droplet using Feynman's path
integral representation of the protons. Examples of charged
nanodroplets that we have studied contain:
Dynamics of chemical reactions in solution
Chemical reactions in solution and phase transitions are examples of
processes of chemical interest that occur at long time scales. Such time
scales cannot be simulated using straightforward Molecular Dynamics
techniques even with the use of the fastest computers. In order to
tackle these problems we employ theories of activated processes. The
study involves the investigation of an appropriate reaction coordinate
(or a set of such coordinates) that describes well the physical process.
The phenomena that are studied are complex and the degrees of freedom
of the environment, for example the solvent, has to be taken into
account in the construction of the reaction coordinate. Reversible work
profiles and sampling of trajectories initiated at the transition state
reveal the reaction mechanism and allow for the computation of the rate.
In addition to this approach for the study of reactions, transition
path sampling methods [L. R. Pratt ``A statistical method for
identifying transition states in high dimensional problems'', J. Chem. Phys.
85(9): 5045-5048 (1986)] are used. We apply the methods in the study of
proton transfer in biological molecules where we use Feynman's path
integral representation of the proton and other mixed quantum-classical
methods.
"Recoil-growth" schemes for high density polymer systems
Polymers are ubiquitous in industrial and technological applications.
Due to the extremely long relaxation times present in high density
polymer systems such systems are impossible to model by conventional
Molecular Dynamics and Monte Carlo methods. The first problem
encountered in the computation of equilibrium and dynamic properties is
the generation of equilibrated configurations. We develop biased Monte
Carlo schemes that allow for rapid equilibration of these complex
systems and we apply these schemes in the study of problems of
biological interest.
Collaborative projects with chemical engineering
In collaboration with groups in chemical engineering, we simulate the
"oiling-out" effect and develop efficient computational schemes that
assist the experimental methods in separation of enantiomers with
applications in drugs and agrochemicals.
Selected Publications:
S. Consta "Manifestation of Rayleigh instability in Droplets containing
multiply charged macroions", J. Phys. Chem. B, 114(16):5263 (2010).
S. Consta "Detecting reaction pathways and computing reaction rates in
condensed phase", Theoretical Chemistry Accounts, 116(1-3):373 (2006).
O. M. Braun, M. Paliy, S. Consta "Ordering of a thin lubricant film due
to sliding", Phys. Rev. Lett. 92 (25): Art. No. 256103 (2004).
S. Consta, K. Mainer and W. Novak "Mechanisms of Fragmentation processes
of droplets charged with ions", Journal of Chemical Physics
119(19):10125 (2003).
S. Consta, N.B. Wilding, D. Frenkel, and Z. Alexandrowitz. "Recoil growth: an efficient simulation method for multi-polymer
systems.'' Journal of Chemical Physics, 110 :3220--3228 (1999).
• several alkali or alkaline earths ions in water or mixture of solvents
• highly charged peptides in water
• sodiated poly(ethylene glycol) polymers with and without water
