-Benjamin R. Barber
“In theory there is no difference between theory and practice. In practice there is.”
“Some people want it to happen, some wish it would happen, others make it happen.”
Our research is in the field of theory and simulation of condensed matter and revolves around application of quantum-mechanical based computational methods to study advanced materials for sustainable energy and device applications. The key focus is on the development of fundamental understanding of atomic-scale mechanisms that govern (nano)materials properties, especially at electrochemical interfaces. To this end, we employ a variety of theoretical methods including density-functional-theory static and molecular dynamics simulations combined with enhanced free-energy sampling techniques, Marcus electron transfer theory, Monte Carlo and ab initio thermodynamics approaches.
Redox Flow Batteries.
Redox flow batteries (RFBs) represent a viable solution for large-scale energy storage applications that are capable of storing large amounts of electrical energy from intermittent renewable sources by electrochemical reactions of redox species dissolved in liquid electrolytes at the active surface sites of electrodes. Despite years of experimental efforts, atomic-scale details about the mechanisms of reactions occurring in the electrolyte solutions and at the electrode surfaces in RFBs, required for further enhancement of energy and power density, are still lacking. We are undertaking systematic first-principles studies to understand both solution and interfacial electrochemistry of RFBs. Our current focus is on the chemistry of vanadium RFBs (V2+/V3+ and VO2+/ VO2+ redox couples) and electrocatalytic properties of carbon-based (graphite, graphene) electrodes for which a wealth of experimental data is available.
Figure on the right shows free-energy profiles for the adsorption-desorption processes between outer- and inner-sphere complexes of aqueous V2+ and V3+ at the edge graphite as simulated using AIMD-based metadynamics.
Jiang Z., Klyukin K. and Alexandrov V. “First-Principles Study of Adsorption-Desorption Kinetics of Aqueous V2+/V3+ Redox Species on Graphite in a Vanadium Redox Flow Battery.”
Physical Chemistry Chemical Physics (Communication) 19, 14897-14901 (2017)
Jiang Z., Klyukin K. and Alexandrov V. “Structure, Hydrolysis and Diffusion of Aqueous Vanadium Ions from Car-Parrinello Molecular Dynamics.”
Journal of Chemical Physics 145, 114303-114311 (2016)
Catalytic Conversion of CO2.
The problem of anthropogenic CO2 emissions has been recently attracting a lot of attention due to a dramatic rise of CO2 in the atmosphere in the last few decades. The design of new catalysts with improved efficiency and selectivity that would enable low-cost CO2 conversion to valuable chemicals is necessary for sustainable carbon-free economics. We aim to contribute to the development of a comprehensive atomistic understanding of CO2 reaction mechanisms over non-metal and metal-oxide based catalysts under realistic reaction conditions.
Klyukin K. and Alexandrov V. “CO2 Adsorption and Reactivity on Rutile TiO2(110) in Water: An Ab Initio Molecular Dynamics Study.”
Journal of Physical Chemistry C 121, 10476–10483 (2017)
Low-Dimensional Ferroelectric Systems.
The control over field-induced polarization switching in ferroelectric-based devices cannot be achieved without detailed understanding of the role of atomistic effects on polarization reversal including structural defects and interfacial (electro)chemical reactions. This atomistic control over ferroelectric behavior will lead to enhanced functionality of the various ferroelectric-based devices such as memories and field-effect transistors. Since the degree to which various defects can affect ferroelectric properties and their role in mediating polarization switching are still not completely understood, we perform first-principles calculations to unveil the interplay between polarization, conductivity and material properties. For example, we demonstrate that both the titanium TiSr and strontium SrTi antisite defects induce ferroelectric polarization in otherwise nonferroelectric SrTiO3, while the magnitude of spontaneous polarization in SrTiO3 can be tuned by controlling the degree of Sr/Ti nonstroichiometry. We are also studying the effect of TiSr antisite in SrTiO3 on the tunneling electroresistance (TER) in asymmetric Pt/SrTiO3/Pt ferroelectric tunnel junctions with an attempt to correlate the computational results with experimental observations (as shown in Figure on the right).
Klyukin K. and Alexandrov V. “Effect of Intrinsic Point Defects on Ferroelectric Polarization Behavior of SrTiO3.”
Physical Review B 95, 035301-035308 (2017)