  We perform density functional molecular dynamics simulations of liquid and
solid MgSiO3 in the pressure range of 120-1600 GPa and for temperatures up to
20000 K in order to provide new insight into the nature of the liquid-liquid
phase transition that was recently predicted on the basis of decaying laser
shock wave experiments [Phys. Rev. Lett. 108 (2012) 065701]. However, our
simulations did not show any signature of a phase transition in the liquid
phase. We derive the equation of state for the liquid and solid phases and
compute the shock Hugoniot curves. We discuss different thermodynamic functions
and by explore alternative interpretations of the experimental findings.
