Ab initio molecular dynamics: Propagating the density matrix with Gaussianorbitals

We propose and implement an alternative approach to the original Car-Parrin ello method where the density matrix elements (instead of the molecular orb itals) are propagated together with the nuclear degrees of freedom. Our new approach has the advantage of leading to an O(N) computational scheme in t he large system limit. Our implementation is based on atom-centered Gaussia n orbitals, which are especially suited to deal effectively with general mo lecular systems. The methodology is illustrated by applications to the thre e-body dissociation of triazine and to the dynamics of a cluster of a chlor ide ion with 25 water molecules. (C) 2001 American Institute of Physics.