  In this work, we investigate calcium titanate (CaTiO3 - CTO) using X-ray
diffraction and Raman spectroscopy up to 60 and 55 GPa respectively. Both
experiments show that the orthorhombic Pnma structure remains stable up to the
highest pressures measured, in contradiction to ab-initio predictions. A fit of
the compression data with a second-order Birch-Murnaghan equation of state
yields a bulk modulus K0 of 181.0(6) GPa. The orthorhombic distortion is found
to increase slightly with pressure, in agreement with previous experiments at
lower pressures and the general rules for the evolution of perovskites under
pressure. High-pressure polarized Raman spectra also enable us to clarify the
Raman mode assignment of CTO and identify the modes corresponding to rigid
rotation of the octahedra, A-cation shifts and Ti-O bond stretching. The Raman
signature is then discussed in terms of compression mechanisms.
