  We present a scheme for the calculation of linear optical properties by the
all-electron full-potential linearized augmented planewave (LAPW) method. A
summary of the theoretical background for the derivation of the dielectric
tensor within the random-phase approximation is provided together with symmetry
considerations and the relation between the optical constants. The momentum
matrix elements are evaluated in detail for the LAPW basis, and the interband
as well as the intraband contributions to the dielectric tensor are given.
Results are presented for the metals aluminum and gold, where we crosscheck our
results by sumrules. We find that the optical spectra can be extremely
sensitive to the Brillouin zone sampling. For gold, the influence of
relativistic effects on the dielectic function is investigated. It is shown
that the scalar-relativistic effect is much more important than spin-orbit
coupling. The interpretability of the Kohn-Sham eigenstates in terms of excited
states is discussed.
