The structures of two samples of gold nanoclusters supported on silica werestudied by X-ray powder diffraction (XRD) and X-ray absorption spectroscopy.The data relative to both techniques were analysed by an approach involvingsimulation based on structural models and fitting. The XRD model concerned adistorted f.c.c. (face-centred cubic) arrangement, with microstrains and parallelstacking faults in approximately spherical particles; as an alternative possibility,a linear combination of ordered f.c.c. and noncrystalline (decahedral andicosahedral) particles was also taken into account. Both approaches gavecalculated patterns closely resembling the experimental data. X-ray absorptionspectra were fitted on the basis of f.c.c. and noncrystalline arrangements. Thebest results were obtained by the f.c.c. motif, while a simulation consisting in thesuperposition of f.c.c. and noncrystalline components in the relative amountsdetermined by XRD analysis gave a poor agreement with the experimental data.It was concluded that the good XRD fitting obtained by linear combination oflognormal size-distributed f.c.c. cuboctahedral, decahedral and icosahedralcontributions was a result of the flexibility of the basis set of functions, but thatthe complementary analysis of X-ray absorption data did not confirm thepresence of a noteworthy fraction of noncrystalline particles.
|Numero di pagine||10|
|Rivista||Journal of Applied Crystallography|
|Stato di pubblicazione||Published - 2008|
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