Adiabaticity in first-principles molecular dynamics

Car-Parrinello-like simulations critically depend on the ability to control the drift of the electronic wave functions away from the instantaneous ground state. This problem, particularly severe for metals, is gaining more importance as the time scale of such simulations increases. Here a method is proposed that solves the problem by introducing two separate thermostats for ions and electrons, without adding to the computational cost. A detailed analysis of the nonadiabatic behavior leads to a strategy that minimizes the resulting errors. An application of the method to molten aluminum is presented.