  Ice-rich planets are formed exterior to the water ice-line and thus are
expected to contain a substantial amount of ices. The high ice content leads to
unique conditions in the interior, under which the structure of a planet is
affected by ice interaction with other metals. We apply experimental data of
ice-rock interaction at high pressure, and calculate detailed thermal evolution
for possible interior configurations of ice-rich planets, in the mass range of
super-Earth to Neptunes (5-15 Earth masses). We model the effect of migration
inward on the ice-rich interior by including the influences of stellar flux and
envelope mass loss. We find that ice and rock are expected to remain mixed, due
to miscibility at high pressure, in substantial parts of the planetary interior
for billions of years. We also find that the deep interior of planetary twins
that have migrated to different distances from the star are usually similar, if
no mass loss occurs. Significant mass loss results in separation of the water
from the rock on the surface and emergence of a volatile atmosphere of less
than 1 percent of the planet's mass. The mass of the atmosphere of water/steam
is limited by the ice-rock interaction. We conclude that when ice is abundant
in planetary interiors the planet structure may differ significantly from the
standard layered structure of a water shell on top of a rocky core. Similar
structure is expected in both close-in and further-out planets.
