research papers
Trirutiles are AB2O6 crystal structures with a tripled c-axis repeat compared to the rutile type, owing to ABBABBA metal ordering. Partially disordered trirutiles, space group P42/mnm, are here described by addition of a sinusoidal scattering density wave along c to the basic rutile structure. As a result of this approach, an infinite number of crystal structures can be envisaged, which pairwise exhibit identical X-ray diffraction patterns, i.e. this is a case where the expected one-to-one relationship between crystal structure and diffraction intensity distribution is replaced by a two-to-one relationship