Nanocluster rotation on Pt surfaces: Twist boundaries

Nanoscale Pt particles situated on a Pt surface are studied by molecular dynamics simulations. It is shown that for the simple case of symmetrical twist boundaries with low index planes, the structure and dynamics of the system are sensitive to finite size effects. Namely, below a specific nanoparticle size the particles will align themselves with the substrate, while for larger particles a stable array of grain boundary dislocations is created. It is shown that nanoparticle rotation is a direct result of athermal slip of the grain boundary dislocations that are created at the part ic le-substrate interface. The size effects are unique to nano-sized particles and thus have not yet been observed in past experiments. The simulations also show that the energy and structure of the boundaries are also affected by the system size.