Figure 1

Selected-area diffraction patterns of PFWO taken along the [001] (a) and [111] (b) directions at different temperatures. Note the presence of the weak superstructural reflections of (½, ½, ½)-type which can be seen at all the investigated temperatures. Strong reflections indicate a dominant 3.97 Å primitive cubic subcell. The figures were obtained by converting each pixel of the frames after subtracting the background into points of reciprocal space using the CMC3dsi program [https://chemmatcars.uchicago.edu/software/].