Ab-initio molecular dynamics studies of molecular systems

Physical Chemistry Laboratory, South Parks Road, Oxford 0X1 3QZ, United-Kingdom and Laboratoire de Physique de l’Ecole Normale Supérieure de Lyon, 46, allée d’Italie, 69364 Lyon Cedex 07, France.

Abstract

The ab-initio molecular dynamics method proposed by Car and Parrinello (C-P) permits the simulation of the dynamical behaviour of large systems for which the total potential energy cannot be expressed as a sum of effective internuclear potentials. Such cases arise when large reorganisations of the valence electrons accompany the nuclear motion, as in many chemical reactions. The C-P method provides an efficient scheme for following the nuclear motion along the adiabatic electronic ground-state potential energy surface, which is calculated "on-the-fly". Stable (energy conserving) molecular dynamics trajectories for tens of picoseconds on systems containing one to two hundred atoms have already been performed. The valence electron rearrangements themselves can be studied as a by-product of the calculation.

The basic ideas underlying the C-P method will be outlined and the properties referred to above will be illustrated by reference to simulations of the isomerisation and dissociation dynamics of small (non-biological) molecules. The prospects for applying the method to systems of biological interest will then be discussed and the developments necessary to allow this generalisation will be highlighted.