Résumé
A reconsideration of Car–Parrinello molecular dynamics using only atom centred basis functions is presented by doing direct propagation of molecular orbitals in conjunction with propagation of nuclei. The electronic degree of freedom chosen for the propagation are the coefficients of the linear combination of atomic orbitals development where atomic orbitals are expressed upon Gaussian functions. Considering that the wave function is propagated, we show that only very few iterations are sufficient to calculate nuclear gradients and electronic potential energy with good accuracy, instead of fulfilling the minimisation energy procedure at each step of the dynamics simulation. First tests calculations are presented by considering simple systems (water and monothiooxalic acid molecules and a (H2O)20 water cluster). These tests present the good behaviour of the propagation scheme if one considers the conservation of the total energy and the accuracy of the potential energy surface compared with Born–Oppenheimer calculations.