First-principles simulations for matter under extreme conditions and
interior of planets and exoplanets

A large number of planets has been found around other stars since 1995
which show a great diversity in mass, chemical composition, and orbital
parameters. For the description of their interior, knowledge on the
behavior of matter under extreme conditions (pressures up to tens of
Mbar and temperatures up to about 100.000 K) is important. Surprisingly,
the high-pressure phase diagram of even the simplest and most abundant
elements hydrogen and helium which are the main constituents of
Jupiter-like planets is not well known. Interesting phenomena such as
proton conduction and phase separation occur in H-C-N-O mixtures at high
pressures as relevant for Neptune-like planets. Knowledge on the
high-pressure phase diagram of minerals of the MgO-FeO-SiO2 complex is
necessary in order to understand the interior of rocky planets like
Earth and super-Earths. The talk gives an overview of first-principles
simulation results on the behavior of these materials under extreme
conditions which are then applied in planetary physics.