  We use electronic structure calculations based upon density functional theory
to search for ideal plasmonic materials among the alkali noble intermetallics.
Importantly, we use density functional perturbation theory to calculate the
electron-phonon interaction and from there use a first order solution to the
Boltzmann equation to estimate the phenomenological damping frequency in the
Drude dielectric function. We discuss the necessary electronic features of a
plasmonic material and investigate the optical properties of the alkali-noble
intermetallics in terms of some generic plasmonic system quality factors. We
conclude that at low negative permittivities, KAu with a damping frequency of
0.0224 eV and a high optical gap to bare plasma frequency ratio, outperforms
gold and to some extent silver as a plasmonic material. Unfortunately, a low
plasma frequency (1.54 eV) reduces its utility in modern plasmonics
applications. We also discuss, briefly, the effect of local fields on the
optical properties of these materials.
