Time-Dependent Density Functional Theory Molecular Dynamics Simulations of Liquid Water Radiolysis

I. TAVERNELLI; M. P. GAIGEOT; R. VUILLEUMIER; C. R. STIA; M. A. HERVÉ DU PENHOAT; M. F. POLITIS

Chemphyschem

Wiley-VCH Verlag GmbH & Co

Año: 2008 vol. 9 p. 2099 - 2103

1439-4235

The early stages of the Coulomb explosion of a doubly ionizedwater molecule immersed in liquid water are investigated with time-dependent density functional theory molecular dynamics (TD–DFT MD) simulations. Our aim is to verify that the double ionization of one target water molecule leads to the formation of atomic oxygen as a direct consequence of the Coulomb explosion of the molecule. To that end, we used TD–DFT MD simulations in which effective molecular orbitals are propagated in time. These molecular orbitals are constructed as a unitary transformation of maximally localized Wannier orbitals, and the ionization process was obtained by removing two electrons from the molecular orbitals with symmetry 1B1, 3A1, 1B2 and 2A1 in turn. We show that the doubly charged H2O(2+) molecule explodes into its three atomic fragments in less than 4 fs, which leads to the formation of one isolated oxygen atom whatever the ionized molecular orbital. This process is followed by the ultrafast transfer of an electron to the ionized molecule in the first femtosecond. A faster dissociation pattern can be observed when the electrons are removed from the molecular orbitals of the innermost shell. A Bader analysis of the charges carried by the molecules during the dissociation trajectories is also reported.