 Solution

Each Ti has coordination number six, with oxygen neighbours forming a distorted octahedron. Each oxygen has coordination number three, with titanium neighbours forming a planar triangle. For oxygen at $(u,u,0)$, the nearest Ti positions can be taken as $(0,0,0)$ and $(1/2,1/2,\pm 1/2)$; all three lie in the plane $x=y$. The triangle is not generally equilateral. Equal Ti–O bond lengths in the following calculation do not make every angle ideal.