Bulk plasmons in elemental metals

The spectral properties, momentum dispersion, and broadening of bulk plasmonic excitations of 26 elemental metals are studied from first principles calculations in the random-phase approximation. Spectral band structures are constructed from the resulting momentum- and frequency-dependent inverse dielectric function. We develop an effective analytical representation of the main collective excitations in the dielectric response, extending our earlier model based on multipole-Padé approximants (MPAs) to incorporate both momentum and frequency dependence [MPA(𝐪)]. With this representation, we identify plasmonic quasiparticle dispersions exhibiting complex features, including nonparabolic energy and intensity dispersions, discontinuities due to anisotropy, and overlapping effects that lead to band crossings and anticrossings. Comparing with available experimental data, mainly in the optical limit, we find good agreement with the computed spectra. The results for elemental metals and their effective MPA(𝐪) representation establish a reference point that can guide both fundamental studies and practical applications in plasmonics and spectroscopy.