Non‐integral phase in tridymite

The non‐integral phase in tridymite was found in the range 150° to 190 °C. The distance between main and satellite reflection along the a*‐axis changed continuously depending on temperature. The non‐integral satellites result from wavy shift of the atomic positions. The average amplitude is estimated to be about 0.3 A from the intensity dependence on sin ϑ/λ. The symmetry operations in four‐dimensional space are as follows: (0,0,0,0), (1/2,1/2,0,0,)+x, y,z,ξ, x, ȳ, 1/2−z, ξ, x, y, z, ?, x, ȳ, 1/2+z, ?. The structure is refined using a newly‐developed program. The non‐weighted R for 81 reflections is 0.16. Atomic displacements tend to form a ditrigonal six‐membered ring in reference to the low temperature structure.