Thermodynamic and kinetic properties of surface dislocations on Au(001) from atomistic simulations

We examined the thermodynamic and kinetic properties of surface dislocations on the Au 001 surface using atomistic simulations based on a modified embedded atom potential that was optimized for Au surfaces. Two different surface dislocations are obtained, containing five displaced atomic columns type I or three displaced atomic columns type II . Both configurations are more stable than adatoms on the surface and type I is more stable than type II surface dislocation. The energy of the surface containing type I surface dislocations decreases with decreasing dislocation spacing, while that containing type II surface dislocations exhibits a minimum at a particular dislocation spacing. The surface stress of surfaces with type I surface dislocations surprisingly increases with decreasing surface dislocation spacing, while the surface stress decreases with decreasing dislocation spacing on surfaces containing type II surface dislocations. We also calculated the activation energies for surface dislocation migration in directions perpendicular and parallel to the surface dislocation line using a string method. The activation energies of both perpendicular and parallel motions are similar, and therefore a surface dislocation can move both parallel and normal to itself. This has been confirmed experimentally. We also found that type II surface surface dislocation corresponds to a metastable structure through which the type I surface dislocation must pass as it migrates perpendicular to its line direction.