Séminaire

Mardi 12 Novembre 2019 à 11h00.

Toward First Principles Simulations of Biological Matter under Ionizing Radiations

''L'équipe L'équipe dynamique multi-echelle des édifices moléculaires invite Aurélien Delalande du Laboratoire de Chimie Physique (Paris-Saclay) .
Abstract. The transient collision (10-17 s) of high-energy-transfer particles with biological matter results in ionization or excitation of its constituent molecules. Huge amounts of energy are deposited locally, typically several tens of eV. These early physical events produce a myriad of reactive radical species that are at the source of cascades of chemical processes spanning several spatial and temporal scales. The physical chemistry of these ultrafast processes are not well understood at the present time. During this seminar I will introduce an original set of methodologies that we have devised to investigate these phenomena from first principles [1,2]. These are based on Real-Time Time-Dependent Density Functional Theory (RT-TDDFT) and Ehrenfest Molecular Dynamics (MD) simulations. A hybrid scheme coupling these approaches to polarizable force fields have been devised to simulate large biological systems. This implementation includes explicit time propagation of the electric fields mediating interaction between the quantum and classical parts of the system[3]. Theses methodologies have been implemented in deMon2k. Our approach allows simulations of collisions of molecules with HET, and subsequent ionization, ultrafast charge migration, energy relaxation/dissipation on the attosecond time scale (cf. Figure). Ehrenfest MD further gives access to non-adiabatic chemical reactivity taking place in the first femtoseconds after irradiation. I will introduce the methodologies and applications to various questions of current high interest in radiation chemistry.
Acknowledgments: We thank the French ANR (ANR-15-CE29-0011-01) and CNRS (projet Emergence@INC, 2018) and GENCI for computational ressources.
[1] Simulating Electron Dynamics in Polarizable Environments. X. Wu, J. -M. Teuler, C. Clavaguéra, F. Cailliez, D. R. Salahub, A. de la Lande, J. Chem. Theor. Comput. 13 (2017) 3985.
[2] Quantum Chemical topology of the Electron Localization Function in the Field of Attosecond Electron Dynamics. A. Parise, A. Alvarez-Ibarra, X. Wu, X. Zhao, J. Pilmé, A. de la Lande, J. Phys. Chem. Lett. 9 (2018) 844.
[3] Retardation in electron dynamics simulations based on time-dependent density functional theory. X. Wu, A. Alvarez-Ibarra, D. R. Salahub, A. de la Lande. Eur. J. Phys. D. 72, (2018), 206
[4] Non-Adiabatic Molecular Dynamics simulations in the framework of Auxiliary Time-Dependent Density Functional Theory. A. Alvarez-Ibarra, K. Hasnaoui,.., A. de la Lande. In preparation.
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