MOLECULAR-DYNAMICS FOR CHEMICALLY BONDED SYSTEMS

The Car-Parrinello molecular dynamics-density functional scheme derives reliable forces from the energy functional of Kohn and Sham. The authors describe an alternative approach based on a related energy functional that can be assigned a value for any density, specifically a superposition of site densities moving with the nuclear sites. 'In-out' fluctuations of the site densities are described by parameters that are treated as dynamical variables in a Lagrangian formulation. An important feature of the scheme is its adaptability with respect to the method used to solve the electronic structure part of the problem. Explicit calculations for the H2 molecule illustrate how the scheme can be used with the electrons described in terms of a localised orbital basis.