AVS 45th International Symposium
    Surface Science Division Thursday Sessions
       Session SS-ThP

Paper SS-ThP29
Computer Simulation of the Au(111) @sr@3 x 22 Surface Reconstruction

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: T.M. Trimble, University of Maryland
Authors: T.M. Trimble, University of Maryland
R.C. Cammarata, Johns Hopkins University
E.D. Williams, University of Maryland
K. Sieradzki, Arizona State University
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A computer simulation study of the Au(111) @sq@3 x 22 surface reconstruction will be discussed. This reconstruction can be described as involving a uniaxial in-plane contraction of the top monolayer corresponding to a surface strain of about 4%, and has been observed to be the stable surface structure at low temperatures. The driving force for this reconstruction has been identified as the difference in the surface stress f and the surface free energy @gamma@ of the 1x1 surface, while the opposing force is owing to the free energy cost associated with the top monolayer losing atomic registry with underlying lattice. A simple continuum analysis gave the following stability criterion: a (111) fcc metal surface will undergo a reconstruction involving contraction of the top monolayer if the ratio (f - @gamma@)/µb exceeds a certain critical value of order 0.1, where µ is the shear modulus and b is the nearest neighbor distance. This criterion was tested with computer simulations that were conducted using the Johnson analytical embedded atom method (EAM) potential. Since the standard Johnson potential for Au leads to the result that the 1x1 surface is stable to reconstruction, modifications were made in values of some Johnson EAM input paramters in order to stabilize the reconstruction. It was found that although the resulting values of f and @gamma@ were somewhat lower than those obtained from first principles calculations, the driving force (f - @gamma@) obtained by the simulation and the first principle calculations were very close. Furthermore, the critical value of the stability parameter (f - @gamma@)/µb, inferred from results obtained from simulations of reconstructions with different surface strains, was found to be very close to that predicted by the continuum analysis. This work was supported by NSF through the University of Maryland MRSEC.