Development of Direct Born–Oppenheimer Molecular Dynamics with Applications to Water Clusters and Mechanochemistry

Abstract

New methods for Born-Oppenheimer molecular dynamics simulations have been developed and used to study protonated water clusters and mechanochemistry of alkanes. The novel algorithms are an efficient coordinate transformation and sampling microcanonical ensembles of trajectories used for generating starting conditions for simulations. In combination with existing techniques as well as with electronic structure methods within DALTON program, they make it a powerful tool to study reaction dynamics, free of charge. This has been demonstrated by investigation of protonated water clusters relevant for water nucleation in atmospheric chemistry. The structure of the proton salvation shell and evaporation kinetics have been revealed. Another application is the dynamics of alkanes under mechanical stress. Short-chain alkanes – butane and octane – are model compounds for polymers. Their dynamical behavior was simulated and analyzed under two scenarios mimicking the modes ofmechanochemical activation: slow stretching in the atomic-force microscope and violent action of ultrasound.