Kinetics of atomic ordering and diffuse scattering of X-rays within the nonstoichiometric quasi-binary (W,Ti)B₂crystal

Abstract

A synthetic specimen of the mineral CaTiSiO 5 has been studied using the time-of-flight neutron diffractometer SXD at ISIS and highenergy X-ray diffraction using 100keV X-rays on BW5 at DESY. Diffuse scattering at room-temperature has been recorded using both techniques. The diffuse features appear rather different in the two datasets owing to the relative scattering power of X-rays and neutrons from the various elements. To model the data, ab-initio phonons have been calculated using density-functional perturpation theory as implemented in CASTEP and reciprocal space maps corresponding to first-order thermal diffuse scattering are compared with the data. Very good visual agreement is obtained with both neutrons and X-rays confirming the thermal nature of the diffuse scattering. The present work provides a basis for studying the diffuse scattering in the high-temperature phase and inelastic spectra away from the zone-centre.