Furthermore, we have performed Rietveld-based structural refinements for x = 0.45, 0.69, 0.85 and 0.96 based on a simplified structural model for extracting the network geometry and framework distortion modes, see SI for the employed strategy of structure refinement (S-59) and for results (Table ). Visual inspection of the PXRD pattern and differences curve of the Rietveld fits suggests that the results should be treated with care; however, for all compounds, Ap lies between 2.013 (x = 0) and 4.232 (x = 1), suggesting tunability of Ap via A + substitution (Fig. ). Thus, by employing the solid solution approach, it is possible to fine-tune B in a window as fine as B = 8.5 (x = 0) -10.5 (x = 1) GPa.