Fig. 7.

Summary of x-ray diffraction patterns. λ = 0.6198 Å. Structures I4/mcm-32 (host–guest) and C2/c-32 (host–guest) have very similar diffraction patterns to C2/m-32 (host–guest) shown here. The absence of several reflections, predicted for the β-tin structure at 40 GPa, in the experimental diffraction pattern, might be explained by preferred orientation with a unique [101] or [111] direction. The experimental diffraction pattern at 139 GPa is explained (as proposed in ref. 2) by a mixture of phases IV and V.