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RESEARCH AREAS       The ANSER Center is a |
Victor Batista |
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Biographical SketchVictor S. Batista was brought up in Buenos Aires. In 1991 he moved to Boston and studied for his doctorate in chemistry, where he worked under the mentorship of Prof. David F. Coker on the development of theoretical and computational methods to investigate photochemical reaction dynamics in the condensed phase. Following two postodoctoral research programs, working on semiclassical methods with Prof. William H. Miller at the University of California, Berkeley (1997–1999) and coherent-control techniques with Prof. Paul Brumer at the University of Toronto (2000-2001), he joined the Yale faculty as an Assistant Professor of Chemistry in 2001. He became Associate Professor of Chemistry in 2005 and since 2008, he is Professor of Chemistry and Director of Undergraduate Studies. He is a member of the American Chemical Society, American Physical Society, and Biophysical Society. Research StatementBatista’s research interests include the development and application of semiclassical and quantum dynamics methods for studies of excited state reaction dynamics and relaxation phenomena in polyatomic systems and semiconductor materials for solar-to-electric energy conversion and photocatalysis. Additionally, he is interested in the development of quantum mechanics/molecular mechanics computational methods to study ligand binding interactions and reactivity in biomolecules, with emphasis on photoreceptors and water-splitting in photosystem II. Time-Dependent Methods: The Batista group has developed time-dependent methods for simulations of quantum reaction dynamics in polyatomic systems, including algorithms based on time-sliced semiclassical and full quantum-mechanical propagators (e.g., the MP/SOFT method). Applications of these methods were focused on ultrafast relaxation processes that produce broad and structureless absorption spectra of polyatomic systems, including nonadiabatic dynamics, excited state intramolecular proton transfer, and photoinduced isomerization processes in excited electronic states. These studies found that the spectral consequence of ultrafast relaxation processes is to mask the structural and dynamical information necessary to describe chemical reactivity at the molecular level, and that computational modeling is essential to provide insight into the nature of reaction dynamics and rigorous assignments of spectroscopic measurements. Thermal Correlation Functions: In addition to quantum dynamics studies based on propagation of multidimensional wavefunctions, the Batista group has generalized the MP/SOFT algorithm to evaluate thermal-equilibrium density matrices, thermal correlation functions, and finite-temperature time-dependent expectation values. The generalized MP/SOFT method exploits the analogy between the time-dependent Schrödinger equation and the Bloch equation and computes finite-temperature density matrices via imaginary-time propagation, avoiding the “sign problem” that usually defies the capabilities of real-time path-integral Monte Carlo. The Heisenberg time-evolution operators, involved in thermal correlation functions, are analogously computed by real-time propagation. Electronic Relaxation in Sensitized Semiconductors: Computational studies of sensitized semiconductor surfaces by the Batista group focused on TiO2 anatase surfaces functionalized with organic and inorganic molecules, including molecular linkers commonly used in Grätzel cells. The studies characterized the nature of interfacial electron transfer mechanisms that for many years have challenged conventional electron transfer theories formulated in the weak-coupling limit. The studies addressed the dynamics of photoinduced electron-hole pair relaxation at the molecular level, and the subsequent carrier diffusion mechanism after electron injection in the conduction band. In addition, coherent control scenarios based on sequences of ultrafast unitary laser pulses were computationally demonstrated, predicting the feasibility of creating and manipulating coherent electronic excitations on monolayers of adsorbate molecules covalently attached to TiO2 semiconductor surfaces. Force Field Parameters: Force field parameters for large-scale computational modeling of sensitized TiO2 surfaces have been developed from the energetic analysis of minimum energy configurations and ensembles of thermal configurations generated by DFT molecular dynamics simulations. The resulting force field, composed of Coulomb, van der Waals and harmonic interactions is an extension of Amber and reproduces ab initio minimum energy structures and phonon spectra density profiles of sensitized TiO2-anatase nanostructures. Furthermore, simulations of interfacial electron injection and electron-hole relaxation dynamics have demonstrated the capabilities of the resulting molecular mechanics force field parameters for accurate modeling nuclear fluctuations responsible for speeding up the interfacial electron transfer dynamics in sensitized semiconductor surfaces at finite temperature. The resulting force field thus offers an opportunity to study models beyond the capabilities of DFT molecular dynamics methods, including adsorbate molecules covalently attached to semiconductor surfaces in complex molecular environments (liquids). Photocatalysis: Computational studies of TiO2 surfaces sensitized with oxomanganese surfaces by the Batista group predicted visible-light sensitization based on TiO2 surface functionalization with oxomanganese complexes. The simulations also suggested the possibility of visible-light photoactivation of Mn catalysts attached to semiconductor surfaces. These results motivated Batista to initiate a collaboration with 3 experimental groups at Yale (including Brudvig, Crabtree and Schmuttenmaer) in a joint experimental and theoretical effort to investigate TiO2 functionalization for solar-light water-splitting and other applications of green-oxidation chemistry in the absence of primary oxidants. The team has already demonstrated, in practice, the feasibility of sensitizing TiO2 to absorption of visible light by surface functionalization with Mn-catalysts, and the possibility of activating Mn(III) catalysts by ultrafast interfacial electron injection. Coherent Control: The Batista group has developed quantum control scenarios for laser manipulation of electronic excitations in sensitized semiconductor surfaces. Building on earlier work on coherent-control of reaction dynamics in excited electronic states, it was found that superexchange hole tunneling through adsorbate molecules can be inhibited and eventually halted by applying sufficiently frequent unitary pulses that exchange energy with the system but do not collapse the coherent evolution, or affect the underlying electron transfer energy barriers. Publications
Most Significant Honors & Awards
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