  This paper describes a new grid for the mass-radius relation of 3-layer
exoplanets within the mass range of 0.1 through 100 Earth Masses. The 3 layers
are: Fe (epsilon iron), MgSiO3 (including both the perovskite phase,
post-perovskite phase, and its dissociation at ultra-high pressures), and H2O
(including Ices Ih, III, V, VI, VII, X, and the superionic phase along the
melting curve). We discuss the current state of knowledge about the equations
of state (EOS) that influence these calculations and the improvements used in
the new grid. For the 2-layer model, we demonstrate the utility of contours on
the mass-radius diagrams. Given the mass and radius input, these contours can
be used to quickly determine the important physical properties of a planet
including its p0 (central pressure), p1/p0 (core-mantle boundary pressure over
central pressure), CMF (core mass fraction) or CRF (core radius fraction). For
the 3-layer model, a curve segment on the ternary diagram represents all
possible relative mass proportions of the 3 layers for a given mass-radius
input. These ternary diagrams are tabulated into Table3 with the intent to make
comparison to observations easier. How the presence of Fe in the mantle affects
the mass-radius relations is also discussed in a separate section. A dynamic
and interactive tool to characterize and illustrate the interior structure of
exoplanets built upon models in this paper is available on the website:
http://www.cfa.harvard.edu/~lzeng
