An X-ray diffraction study of soft surface vibrations of FCC fine metal particles

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Abstract
The lattice parameter and the characteristic temperature theta p of the fine crystalline particles of copper, silver, gold and lead in a range from 60 to 2000 AA in diameter were determined by the X-ray diffraction method. The lattice parameters did not change appreciably from the bulk value in contrast to the observations by electron diffraction by Vermaak and Kuhlmann-Wilsdorf (1968) and by Solliard and Buffat (1977). The characteristic temperature theta p of copper, silver and gold decreases with decreasing particle size. This is due to the softening of the thermal vibration of surface atoms in fine metal particles. The surface characteristic temperature theta s was estimated from the particle size dependence of theta p on the assumption that the effective thickness of the surface is of the order of one atomic layer. The results were in good agreement with LEED experiments. However, theta p of lead particles was not found to change with the decrease of particle size.