- Postdoctoral Scholar (2009-2011), Stanford University (Todd J. Martinez)
- Postdoctoral Fellow (2006-2008), Australian National University (Peter M.W. Gill)
- Ph.D. (2005), Iowa State University (Mark S. Gordon)
- Candidate of Science (2003), Kirensky Institute of Physics (Pavel V. Avramov, Sergey G. Ovchinnikov)
- B.S. (1999), Siberian State Aerospace University
Our research centers on application and development of electronic structure theory and molecular dynamics. The main areas of interest are catalytic properties of metal nanoclusters, coherent control of chemical reactions and electronic structure methods for strongly correlated electrons.
Biological and bio-inspired hydrogen catalysis. Molecular hydrogen is considered to be an ideal “green” energy carrier and potential transportation fuel. However, for large scale use, a cost-effective and carbon-free method for hydrogen production and cleavage must be developed. One way to do this is to replace expensive platinum catalysts, traditionally used in fuel cells, with catalysts based on more common transition metals. In biological systems, hydrogen production and cleavage are catalyzed by the class of metalloenzymes called hydrogenases. The active sites of hydrogenases contain small iron or nickel-iron clusters. Therefore, a promising approach toward developing a low-cost transition metal catalyst would be to utilize some functional model (mimic) of hydrogenases. Theoretical methods are invaluable for giving insight into the mechanisms of these catalytic reactions. The goal of the project is to elucidate the fundamental mechanisms of catalytic hydrogen cleavage and production using high-level ab initio electronic structure and molecular dynamics methods.
Figure 1. Hydrogenases and their active sites models: [FeFe]-hydrogenase (a) and [NiFe]-hydrogenase (b).
Coherent control of chemical reactions. Control of chemical reactions with lasers has been a dream of chemists for many years. We are interested in the development of computational methods which can be used to uncover the physical processes behind coherent control experiments. The goal of a typical coherent control method is to find a laser field which "guides" a molecular system from state X to state Y. To achieve this we are integrating ab initio molecular dynamics methods with local and global control schemes. The new computational methods will be applied to control of unimolecular photodissociation reactions, yield increase in simple bimolecular reactions, and selective chemical bond rearrangement under strong-field conditions.
Figure 2. Pump-dump scheme: a simple example of coherent control. By changing the time interval between laser pulses (vertical yellow lines), it is possible to "guide" the dissociation of molecule ABC to products A+BC (a) or AB+C (b).
Explicitly correlated electronic structure methods. Many interesting and potentially important molecules and clusters can not be accurately described by modern electronic structure methods due to the presence of strongly correlated electrons. Examples of such systems include transition metal clusters, transition states of chemical reactions and excited electronic states. We recently proposed an approach based on variational optimization of a traditional MCSCF wave function multiplied by a Jastrow factor, represented by two-electron geminals. This explicitly correlated method is capable of recovering a significant fraction of the correlation energy and accelerating convergence with respect to the size of the one-electron basis at the same time. It is expected to provide a long-sought reliable electronic structure method for multistate molecular dynamics and coherent control simulations.
Figure 3. Pople diagram demonstrating the relation between size of one-electron basis and electronic structure methods. Explicitly correlated methods are able to "access a diagonal" directly, recovering electron correlation and accelerating convergence with respect to the one-electron basis.
- Zaari, R.R.; Varganov, S.A. Nonadiabatic Transition State Theory and Trajectory Surface Hopping Dynamics: Intersystem Crossing Between 3B1 and 1A1 States of SiH2. J. Phys. Chem. A 2015, 119, 1332-1338.
- Kaliakin, D.S.; Zaari, R.R.; Varganov, S.A. Effect of H2 Binding on the Nonadiabatic Transition Probability between Singlet and Triplet States of the [NiFe]-Hydrogenase Active Site. J. Phys. Chem. A 2015, 119, 1066-1073.
- Ahmadvand, S.; Zaari, R.R.; Varganov, S.A. Spin-forbidden and spin-allowed cyclopropenone (c-H2C3O) formation in interstellar medium. Astrophys. J. 2014, 795, 173/1-173/5, 5 pp.
- Gaenko, A.; DeFusco, A.; Varganov, S.A.; Martinez, T.J.; Gordon, M.S. Interfacing the Ab Initio Multiple Spawning Method with Electronic Structure Methods in GAMESS: Photodecay of trans-Azomethane. J. Phys. Chem. A 2014, 118, 10902-10908.
- Lykhin, A.O.; Novikova, G.V.; Kuzubov, A.A.; Staloverova, N.A.; Sarmatova, N.I.; Varganov, S.A.; Krasnov, P.O. A complex of ceftriaxone with Pb(II): synthesis, characterization, and antibacterial activity study. J. Coord. Chem. 2014, 67, 2783-2794.
- Fedorov, D.A.; Derevianko, A.; Varganov, S.A. Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers. J. Chem. Phys. 2014, 140, 184315.
- Yson, R.L.; Gilgor, J.L.; Guberman, B.A.; Varganov, S.A. Protein induced singlet-triplet quasidegeneracy in the active site of [NiFe]-hydrogenase. Chem. Phys. Lett. 2013, 577, 138-141.
- Kumar, B.; Viboh, R.L.; Bonifacio, M.C.; Thompson, W.B.; Buttrick, J.C.; Westlake, B.C.; Kim, M.-S.; Zoellner, R.W.; Varganov, S.A.; Mörschel, P.; Teteruk, J.; Schmidt, M.U.; King, B.T. Septulene: The Heptagonal Homologue of Kekulene. Angew. Chem., Int. Edit. 2012, 51, 12795-12800.
- Varganov, S.A.; Martinez, T.J. Variational geminal-augmented multireference self-consistent field theory: Two-electron systems. J. Chem. Phys. 2010, 132, 054103.
- Varganov, S.A.; Gilbert, A.T.B.; Gill, P.M.W. A generalized Poisson equation and short-range self-interaction energies. J. Chem. Phys. 2008, 128, 241101.
- Varganov, S.A.; Gilbert, A.T.B.; Deplazes, E.; Gill, P.M.W. Resolutions of the Coulomb operator. J. Chem. Phys. 2008, 128, 201104.
- Varganov, S.A.; Dudley, T.J.; Gordon, M.S. Predicted IR spectra of Ti8C12 and Ti8C12+. Chem. Phys. Lett. 2006, 429, 49-51.
- Varganov, S.A.; Gordon, M.S. Effects of strong electron correlations in Ti8C12 Met-Car. Chem. Phys. 2006, 326, 97-106.
- Olson, R.M.; Varganov, S.; Gordon, M.S.; Metiu, H.; Chretien, S.; Piecuch, P.; Kowalski, K.; Kucharski, S.A.; Musial, M. Where does the planar-to-nonplanar turnover occur in small gold clusters? J. Am. Chem. Soc. 2005, 127, 1049-1052.
- Rintelman, J.M.; Adamovic, I.; Varganov, S.; Gordon, M.S. Multi-reference second-order perturbation theory: How size consistent is "almost size consistent"? J. Chem. Phys. 2005, 122, 044105.
- Varganov, S.A.; Olson, R.M.; Gordon, M.S.; Metiu, H. The interaction of molecular hydrogen with small gold clusters. J. Chem. Phys. 2004, 120, 5169-5175.
- Varganov, S.A.; Olson, R.M.; Gordon, M.S.; Metiu, H. The interaction of oxygen with small gold clusters. J. Chem. Phys. 2003, 119, 2531-2537.
- Varganov, S.A.; Avramov, P.V.; Ovchinnikov, S.G.; Gordon, M.S. A study of the isomers of C36 fullerene using single and multireference MP2 perturbation theory. Chem. Phys. Lett. 2002, 362, 380-386.