  Motivated by recent experimental measurements on pressure-driven phase
transitions in Mott-insulators as well as the new iron pnictide
superconductors, we show that first principles Car-Parrinello molecular
dynamics calculations are a powerful method to describe the microscopic origin
of such transitions. We present results for (i) the pressure-induced insulator
to metal phase transition in the prototypical Mott insulator TiOCl as well as
(ii) the pressure-induced structural and magnetic phase transitions in the
family of correlated metals $A$Fe$_2$As$_2$ ($A$=Ca,Sr,Ba). Comparison of our
predictions with existing experimental results yields very good agreement.
