Past exam of the materials science course of the University of Cambridge / 2022 / Paper 1 / 1 / d

In the tetragonal crystal system, physical squared distances use $a^2(\Delta x^2+\Delta y^2)+c^2\Delta z^2$. Two Ti–O distances from the corner Ti have length $\sqrt{2}ua$; the other four have length $\sqrt{2a^2(1/2-u{)}^2+c^2/4}$. Equating both to $r$ givesThus, within the equal-bond model,The rutile structure remains tetragonal and its octahedral angles remain distorted; these numbers are not a claim about measured ambient-pressure lattice parameters.