Authors: M. Namkung and R.A. Wincheski
Affilation: NASA Langley Research Center, United States
Pages: 85 - 88
Keywords: molecular dynamics (MD) simulation, surface reconstruction, surface orientational phase transition, surface thermal expansion
We have studied thermal expansion of the surface layers of the hexagonally reconstructed Au (001) surface using a classical Molecular Dynamics (MD) simulation technique with an Embedded Atomic Method (EAM) type many-body potential. We find that the top-most hexagonal layer contracts as temperature increases whereas the second layer expands or contracts depending on the size of system. The expansion coefficient of the top layer is much larger than the other layers, and the calculated thermal expansion coefficients are about and. The Fast Fourier Transform (FFT) image of the atomic density shows that there exists a rotated domain of the top-most hexagonal cluster with rotation angle close to 18 at temperature T < 1000K. As the temperature increases this domain undergoes a surface orientational phase transition. These predictions are in a good agreement with previous phenomenological theories and experimental studies.