Transverse composition waves in rutiles quenched from near the melting point

Three distinct long‐wavelength transverse modulated crystallographic shear surfaces are observed in Fe‐doped rutiles. High‐resolution images and electron and X‐ray diffraction patterns allow the intergrowth structures and reaction mechanisms to be derived. The composition waves represent oscillations within an elastic strain energy potential well produced by the pronounced Young’s modulus minimum along q (020). Phonon dispersion curves of rutile show evidence for softening of the Λ3 TA mode at q (0,0.22,0); this coincides with the centre of the range of incommensurate superlattice spacings observed for the composition waves.