  Using the extended discrete interaction model we investigate the tuneabilty
of surface plasmon resonance in alloys and core-shell nanoparticles made from
silver and gold. We show that the surface plasmon resonance of these alloys and
core-shell particles to a large extent follow Vegard's law irrespective of the
geometry of the nanoparticle. We show the evolution of the polarizability with
size and demonstrate the highly non-linear behaviour of the polarizability with
the ratio of the constituents and geometry in alloys and core-shell
nanoparticles, with the exception for nanorod alloys. A thorough statistical
investigation reveals that there is only a small dependence of the surface
plasmon resonance on atomic arrangement and exact distribution in a
nanoparticle and that the standard deviation decrease rapidly with the size of
the nanoparticles. The physical reasoning for the random distribution algorithm
for alloys in discrete interaction models is explained in details and verified
by the statistical analysis.

Optics;Mesoscale and Nanoscale Physics