  "Astronomical" or "circumstellar" silicate optical functions (real and
imaginary indices of refraction n and k have been previously derived from
compositionally and structurally disparate samples; past values were compiled
from different sources in the literature, and are essentially kluges of
observational, laboratory, and extrapolated or interpolated values. These
synthetic optical functions were created because astronomers lack the
quantitative data on amorphous silicates at all wavelengths needed for
radiative transfer modeling. This paper provides optical functions that (1) are
created with a consistent methodology, (2) use the same sample across all
wavelengths, and (3) minimize interpolation and extrapolation wherever
possible. We present electronic data tables of optical functions derived from
mid-ultraviolet to far-infrared laboratory transmission spectra for two
materials: iron-free glass with chondritic/solar atmospheric abundances, and
metallic iron. We compare these optical functions to other popular n, k data
used to model amorphous silicates (e.g., "astronomical" or "circumstellar"
silicate), both directly and in application to a simple system: the dust shell
of the post-AGB star HD161796. Using the new optical functions, we find that
the far-IR profile of model SEDs are significantly affected by the ratio of
glass to iron. Our case study on HD161796 shows that modeling with our new
optical functions, the mineralogy is markedly different from that derived using
synthetic optical functions and suggests a new scenario of crystalline silicate
formation.
