Dislocation morphology and nucleation within compressed Si nanospheres: A molecular dynamics study

Large scale molecular dynamics simulations of the compression of silicon nanospheres were performed with the Stillinger-Weber potential. Several defects were observed to cause the yielding, including dislocations, stacking faults and phase transformations. To better investigate dislocation interactions, spheres of increasing size comprised of up to one million atoms were simulated. The morphologies of the defects and the conditions under which they are formed are explored. A new and interesting route to dislocation formation is identified and examined in which perfect dislocations form on {1 1 0} planes as opposed to the expected {1 1 1} planes. The dislocations on {1 1 0} planes are observed to form through a pathway with an intermediate metastable state corresponding to a change in the atomic bonding. Density Functional based Tight Binding calculations reveal the feasibility of this pathway although the appearance of dislocations on the {1 1 0} plane in the molecular dynamics simulations is specific to the Stillinger-Weber potential.