Dynamical behaviour of Si clusters studied in real time: Fragmentation and melting

This study analyzes the evolution of silicon clusters of size N up to 70 atoms determined by the increase of the kinetic energy and the resulting transient is constructed using either isoenergic or isothermal molecular dynamics with a quantum mechanical Hamiltonian within the DFT and the semiempirical groups. The calculations show that, while the path to the final stage depends on the type, isoenergic or isothermal, of molecular dynamics the final stage itself is determined only by cluster size and by the input kinetic energy. Fragmentation is observed at all sizes: at N lower than 20 the fragments are monomers, dimers and trimers whereas at the larger sizes subunits of a size in the range of the parent clusters are observed. The results obtained with different Hamiltonians have only quantitative differences, of scarce physical meaning.