The relaxed conventional unit cell can be seen in Figure , together with the TiO 5 S and YO 4 S 5 units. Compared to the experimental structure by Hyett et al. (I4/mmm, a=3.770 Å, c=22.806 Å), the volume of the unit cell decreased by 1.3% (PBEsol; I4/mmm, a=3.755 Å, c=22.682 Å) and 0.5% (HSE06; I4/mmm, a=3.756 Å, c=22.871 Å). The calculated lattice parameters clearly agree well with the experimental data, with slight differences between the two functionals in the out-of-plane c parameter.