Fig. 1: Crystal habit and structure, and phase transition between forms I and II of GN.
From: Exceptionally high work density of a ferroelectric dynamic organic crystal around room temperature
a Typical prismatic crystal habit of form I obtained by crystallization from solution. b ORTEP diagram of the main hydrogen bonding motif in the crystal structure at 250 K. The thermal ellipsoids of the non-hydrogen atoms are shown at the 50% probability level. c Crystal structure of form I viewed in the [001] direction. The hydrogen bonds are shown as dotted lines. d Thermal effects accompanying the transition between forms I and II recorded by DSC (two thermal cycles are shown). Note the offset in the maximum transition temperature between the two cycles. e, f Changes in size and shape of single crystals of GN taken twice over the phase transition. Crystals converted from form I to form II by heating (e) and from form II to form I by cooling (f) between 260 and 310 K are shown. Note that the crystal does not show any visible deterioration. g, h, i Crystal packing comparison of the form I (g), partially converted crystal (h) form II (i) and analyzed by single crystal X-ray diffraction. Scale bars: e 300 µm, f 200 µm.
