  We investigate the crystal structure of YTiO3 at high pressures up to 30 GPa
by synchrotron x-ray powder diffraction (T = 295 K). The variation of the Ti--O
bond lengths with pressure evidences a distinct change in the distortion of the
TiO_6 octahedra at around 10 GPa, indicating a pressure-driven spatial
reorientation of the occupied Ti 3d(t_2g) orbitals. The pressure-induced
reduction of the optical band gap of YTiO3 is determined quantitatively by
mid-infrared synchrotron micro-spectroscopy and discussed in terms of bond
length and orbital orientation changes.
