Hot electrons generated from the decay of localized surface plasmons in metallic nanostructures
have the potential to transform photocatalysis, photodetection and other optoelectronic applications.
However, the understanding of hot-carrier generation in realistic nanostructures, in particular the
relative importance of interband and intraband transitions, remains incomplete. Here we report
theoretical predictions of hot-carrier generation rates in spherical nanoparticles of the noble metals
silver, gold and copper with diameters up to 30 nanometers consisting of more than one million
atoms obtained from an atomistic linear-scaling approach. As the nanoparticle size increases the
relative importance of interband transitions from d-bands to sp-bands relative to surface-enabled spband to sp-band transitions increases. We find that the hot-hole generation rate is characterized by
a peak at the onset of the d-bands, while the position of the corresponding peak in the hot-electron
distribution can be controlled through the illumination frequency. In contrast, intraband transitions
give rise to hot electrons, but relatively cold holes. Importantly, increasing the dielectric constant
of the environment removes hot carriers generated from interband transitions, while increasing the
number of hot carriers from intraband transitions. The insights resulting from our work enable the
design of nanoparticles for specific hot-carrier applications through their material composition, size
and dielectric environment.