a Otto-Schott-Institut, Friedrich-Schiller-Universität, Fraunhoferstraße 6, D-07743 Jena, Germany
b Lehrstuhl für Kristallographie, Institut für Physik, Humboldt-Universität zu Berlin, Invalidenstraße 110, D-01115 Berlin, Germany
Abstract:
Incommensurate modulations in Ba2TiSi2O8, Sr2TiSi2O8, and Ba2TiGe2O8 are compared based on their corresponding electron diffraction patterns. The dependence of the modulations on chemical composition provides a suitable model system for the investigation of incommensurations in framework structures using high-resolution transmission electron microscopy (HRTEM). A widening of quantitative HRTEM utilising the concept of rigid units is proposed allowing for a determination of atomistic displacements responsible for the formation of incommensurately modulated structures.