  Hot electrons and holes generated from the decay of localized surface
plasmons in metallic nanoparticles can be harnessed for applications in solar
energy conversion and sensing. In this paper, we study the generation of hot
carriers in large spherical gold-silver alloy nanoparticles using a recently
developed atomistic modelling approach that combines a solution of Maxwell's
equations with large-scale tight-binding simulations. We find that hot-carrier
properties depend sensitively on the alloy composition. Specifically,
nanoparticles with a large gold fraction produce hot carriers under visible
light illumination while nanoparticles with a large silver fraction require
higher photon energies to produce hot carriers. Moreover, most hot carriers in
nanoparticles with a large gold fraction originate from interband transitions
which give rise to energetic holes and "cold" electrons near the Fermi level.
Increasing the silver fraction enhances the generation rate of hot carriers
from intraband transitions which produce energetic electrons and "cold" holes.
These findings demonstrate that alloy composition is a powerful tuning
parameter for the design of nanoparticles for applications in solar energy
conversion and sensing that require precise control of hot-carrier properties.
