Figure 4 : Different solid-solid transitions occur depending on osmotic pressure and superball shape.

From: Observation of solid–solid transitions in 3D crystals of colloidal superballs

Figure 4

(a) 2D μrad-SAXS patterns for the superballs with m=3.0 of the crystalline sediment at different heights, z, in the capillary, together with schematic representation of the different crystal phases that are found; a plastic crystal (PC), a rhombic crystal with hollow-site stacking (HRC) and a rhombic crystal with bridge-site stacking (BRC). (b) q-positions of the two brightest hk0 peaks in the patterns of (a), indicating a structural transition. (c) The structural angle, β, and ratio of the lattice spacing and the superball edge-to-edge length, d/L, for the different heights in the sediment showing that the structure goes from a low density hexagonal (β60°) structure to a more densely packed rhombohedral (β>60°) structure further down in the sediment. (d) Relative pressure given by −z/Lg versus angle β found for the different superballs, showing the presence of phase transitions in almost all sediments. Note that the −z/Lg scale is reverted such that the top of the graph corresponds to the sediment top and the lines are a guides to the eye. (e) Experimental phase diagram established for the studied superball shapes, where a PC phase (light blue) transforms into a HRC phase (pink) or a BRC phase (dark blue) depending on the superball m. Circles with uniform filling are for hard superballs while particles with m=3.0 have slightly softer interactions. The overall phase transitions are guides to the eye.