The chemical reactions which take place at the surface of the ice particles which compose polar stratospheric clouds, are very important in atmospheric science.  They cause, for example, the ozone depletion problem [1].  These reactions are known to be enhanced by the presence of electrons generated by cosmic rays.  We are studying with ab-initio Molecular Dynamics using the FPMD code, the implication(s) of an electron in excess on the ice surface at stratospheric temperature (T~150K).  In order to describe correctly the charge density of the excess electron, we found that it is necessary to introduce a self-interaction correction (SIC).  We implemented the SIC proposed by Mauri & coworkers [2], which was tested in the case of a single H2O- ion.  Excess electrons are known to stay at the surface of small water clusters, while they become completely solvated (internal states) in larger clusters and in bulk liquid water [3].  At the (0001) surface of ice Ih, we have found that the excess electron preferentially stays at the surface, at least up to a few ps of simulation. The excess e-, however, influences drastically the structure of the first bilayer, in order to increase the number of dangling -OH  bonds pointing outside the surface.  We compare these results with the dynamics of the neutral (0001)-surface, at the same temperature conditions.
[1] Q.-B. Lu and L. Sanche, Phys. Rev. Lett. 87 (2001) 078501; Q.-B. Lu and T. Madey Surf. Sci. 451 (2000) 238; Q.-B. Lu and L. Sanche, J. Chem Phys. 120 (2004) 2434.
[2] M. d'Avezac, M. Calandra and F. Mauri, submitted to PRL
[3] K.D. Jordan Science 306 (2004) 618; D. Hern-Paik et al. ScienceExpress (Sept. 2004) 1102827; A.E. Bragg ScienceExpress (Sept. 2004) 1103527; N.I. Hammer et al. ScienceExpress (Sept. 2004) 1102792