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First Principles Simulations of Biological Matter under Ionizing Radiations

Dr. Aurélien de laLande ( Université Paris Saclay)

Category: Séminaires de l'équipe CT

Lieu et heure:Bibliothèque recherche, 3 eme étage, bâtiment Lavoisier, 14h.

Intervenant: : Dr. Aurélien de la Lande


Laboratoire de Chimie Physique, CNRS – Université Paris-Saclay



First Principles Simulations of Biological Matter under Ionizing Radiations


The transient collision (10-16 s) of high-energy-transfer particles with biological matter results in ionization or excitation of its constituant 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.

In this presentation I will introduce an original set of methodologies that we devised to investigate these phenomena as realistically as possible[1,2]. They are based on Real-Time Time-Dependent Density Functional Theory (RT-TDDFT), Ehrenfest Molecular Dynamics (MD) simulations and polarizable force fields. The methodology has been implemented in the deMon2k program and is very efficient thanks to the use of auxiliary fitted densities. Our approach allows the simulation of collisions of molecules with HET, including retardation effects[3], and subsequent ionization, ultrafast charge migration, or energy relaxation/dissipation on the attosecond time scale (cf. Figure). We can simulate the peculiar ultrafast reactivity within a few picoseconds after collision.

I will show applications to irradiated DNA bases in vacuum and in condensed phase. I will focus essentially on the effect of the microenvironment of the guanine (sugar-phosphate group, hydrogen-bonded cytosine, first hydration layer …) and on the conditions of irradiation (energy of incident alpha particle, angle of impact) on the relaxation mechanisms following collision. The outcomes of these simulations shed new light on the irradiation of DNA by high-energy-transfer particles.

Acknowledgments: We thank the French ANR (ANR-15- CE29-0011-01) and CNRS (projet Emergence@INC, 2018).

[1] X. Wu, J. -M. Teuler, C. Clavaguéra, F. Cailliez, D. R. Salahub, A. de la Lande, J. Chem. Theor. Comput. 13 (2017) 3985.

[2] A. Parise, A. Alvarez-Ibarra, X. Wu, X. Zhao, J. Pilmé, A. de la Lande, J. Phys. Chem. Lett. 9 (2018) 844.

[3] X. Wu, A. Alvarez-Ibarra, D. R. Salahub, A. de la Lande. Eur. J. Phys. D. in press.


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