Solidification of Pb pre-covered Cu(111) surface

  • Authors:

  • E. Vamvakopoulos;G. A. Evangelakis;D. G. Papageorgiou

  • Affiliations:

  • Department of Physics, University of Ioannina, P.O. Box 1186, 45110 Ioannina, Greece;Department of Physics, University of Ioannina, P.O. Box 1186, 45110 Ioannina, Greece;Department of Materials Science and Engineering, Laboratory of Computational Materials Science, University of Ioannina, P.O. Box 1186, 45110 Ioannina, Greece

  • Venue:
  • ICCMSE '03 Proceedings of the international conference on Computational methods in sciences and engineering
  • Year:
  • 2003

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Abstract

We present Molecular Dynamics simulation results based on a semi-empirical potential model in analogy to the Tight Binding scheme in the second moment approximation, concerning the Pb overlayer behaviour deposited on the Cu(111) surface as a function of concentration. We found that the adlayer's character changes from fluid to solid as the Pb concentration passes a characteristic value θc=37.5%. Specifically, for concentration less than θc the deposited Pb atoms exhibit the behaviour of a dilute fluid, while above θc 2D liquid like character appears, to recover typical solid behaviour above the saturation concentration that is dictated from the lattice mismatch at θs=56.3%. These conclusions are deduced from the calculated structural and diffusive properties of the overlayer, namely the Pb lattice parameter and its relative relaxed positions with respect to the bulk lattice spacing as well as the atomic diffusion coefficient. It is found that for concentrations up to θc the adlayer exhibits important expansion with Pb atoms flowing over the substrate and diffusing very fast, while at θs the Pb adlayer is compressed by as much as - 2.65% with respect to the lattice spacing of the bulk Pb material, in agreement with experimental findings.