SIMULATION OF SILICON CLUSTERS FROM QUANTUM LANGEVIN MOLECULAR-DYNAMICS

We present a simulation method to determine from first principles the structure of low symmetry atomic systems. Our method is based on Langevin molecular dynamics and quantum mechanical interactions derived from ab initio pseudopotential calculations. The molecular dynamics time step with this approach can be one to two orders of magnitude larger than in the Car-Parrinello method, compensating for the time required for self-consistency at each step. Moreover, because the simulation is constrained to reside on the Born-Oppenheimer surface, this method can be used for insulating as well as metallic and charged systems. Application will be made to small silicon clusters.