Fig. 5.
The moment transfer is M = 4πsin(θ)/λ. (A) Observed (open black circle) and calculated (red solid line) powder diffraction intensities of FeSe0.88 at 300 K using space group P4/nmm. The Inset in A shows a single peak of the (2, 2, 0), (2, 0, 3), (2, 2, 1) reflection at room temperature. But double peaks show up for (2, 2, 0) and (2, 2, 1) at low temperature, as seen in B. The double-peak structure begins to show up at ≈105 K. Inset in B shows the temperature dependence of the γ angle fit with P-1 symmetry.