Unifying Concepts in Catalysis
Mission and Research Topics
Our research focuses on theoretical modeling of catalysts and catalytic processes. Two important ingredients of any catalytic process are the catalytic centers, and the catalytic cycle of interconnected chemical reactions involving these centers. The catalytic centers can be viewed as reactive transient chemical species that are being consumed and regenerated in the course of the catalytic cycle. For example, transition metal atoms exposed at a surface can easily change their oxidation state at proper conditions. During catalytic cycle, such centers reversibly accept or donate electrons to reactants, effectively reducing reaction barriers. In another example, a metal cation in an ionic compound is replaced by a metal atom that prefers to have a different oxidation state (Li replacing Mg in MgO). In this case, different oxidation states of the surrounding anions can be reversibly accessible at certain conditions.
Such transient reactive species pose a great challenge for modern electronic structure theory. Relevant energy differences are small, and accurate treatment of electron correlation effects becomes crucial. Moreover, the very existence of catalytic centers under realistic temperature and pressure (TP) conditions is a result of statistical interplay of many chemical reactions, such as competitive adsorption and desorption processes at a gas-solid interface. Different TP conditions can drastically change the nature of the catalytic centers, making them especially difficult to treat with standard electronic structure methods.
We aim at developing theoretical methods that allow to address these challenges, and understanding general rules that govern catalytic processes in different systems. We address the problem of including electronic correlation effects in extended systems by combining density functional theory (DFT) with wave-function-based quantum chemistry methods (HF, MP2, CCSD). In order to capture the statistical effects, we employ the ab initio atomistic thermodynamics approach, and kinetic Monte Carlo simulations.