SIZE DEPENDENCE OF THE LATTICE-PARAMETER OF SMALL PALLADIUM PARTICLES

Small palladium particles with mean diameters ranging from 1.4 to 5 nm have been prepared within a plasma polymer matrix from a vinyltrimethylsilane monomer. Electron diffraction has shown a decrease of the Pd lattice parameter with decreasing size of palladium cluster. These experimental data are used to deduce the value of the surface stress coefficient f=6.0±0.9 N/m. A contraction of the lattice constant of small palladium particles with decreasing of cluster size, to our best knowledge, has not been reported in the literature up to now. The results suggest that the dilatation of the Pd lattice constant, often reported in the literature, can be explained in terms of incorporation of impurities like carbon, hydrogen, and oxygen, or pseudomorphism in the case of crystalline supports. © 1995 The American Physical Society.