Ab initio molecular dynamics:: Propagating the density matrix with Gaussian orbitals.: II.: Generalizations based on mass-weighting, idempotency, energy conservation and choice of initial conditions

A generalization is presented here for a newly developed approach to ab initio molecular dynamics, where the density matrix is propagated with Gaussian orbitals. Including a tensorial fictitious mass facilitates the use of larger time steps for the dynamics process. A rigorous analysis of energy conservation is presented and used to control the deviation of the fictitious dynamics trajectory from the corresponding Born-Oppenheimer dynamics trajectory. These generalizations are tested for the case of the Cl-(H2O)(25) cluster. It is found that, even with hydrogen atoms present in the system, no thermostats are necessary to control the exchange of energy between the nuclear and the fictitious electronic degrees of freedom. (C) 2001 American Institute of Physics.