Abstract

While extremely powerful atomistic simulation methods based on molecular dynamics rely heavily on the accuracy with which the interatomic forces are described. This was traditionally done by resorting to empirical potentials. While these potentials have proved to be extremely useful they are challenged to describe complex interactions or chemical processes. During the last odd twenty-five years much progress has been done and ab-initio molecular dynamics in which the interatomic forces are calculated on the fly form accurate electronic structure calculation has become more and more a viable alternative to the standard approach. Ab-initio molecular dynamics circumvents the empirical construction of effective potential, offers predictive power and give full access to the electronic properties.

We shall illustrate the power of this approach by discussing its application to a subtle and elusive systems as water. In addition we shall show how water ions H+ and OH- diffuse and recombine in liquid water. These processes are of course of great relevance in biology, chemistry and electrochemistry. Diffusion of these species proceed via a sequence of bond-forming bond-breaking which requires use of the ab-initio approach.