We have studied the thermodynamic and kinetic growth mechanisms behind the formation of the "pancake" decahedron (D_h) gold nanoparticie using computer simulation.Free energy calculations showed that the full pancake morphology is thermodynamically unstable across all the nanoparticie size ranges studied.However,from observations of growth simulations we discovered that a kinetic transport mechanism plays a significant contributing role in the formation process through a transfer of adatoms from the top and bottom (111) D_h faces to the side (100) faces.More specifically we observed how diffusing adatoms on the (111) face are at times "pulled" off this face and into the (111)-(100) edge of the D_h,forcing a row of (100) side atoms into a (1X5) hexagonal reconstruction.Subsequently,this row of atoms was observed to buckle and then deconstruct forcing adatoms out onto the (100) side face completing the transfer.This transport mechanism is shown to be the main kinetic driving force behind the growth of the thermodynamicaily unstable pancake D_h nanoparticie.The observed mechanism has implications for the nonequilibrium morphologies of nanoparticles involving a (100)-(111) surface boundary,especially for systems with surface reconstructions which increase the density of the surface.
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