Figure 2. A 2D representation of powder diffraction data collected as a function of temperature in coronene.

The top is an indexed, γ-coronene powder pattern to indicate peak positions. Temperature is decreased from 300 K to 12 K and then warmed back to 300 K (top to bottom). Green arrows indicate the emergence of the additional reflections due to β-coronene. Asterisks indicate the temperature at which the β-phase becomes detectable (blue) and drops back into the noise (red). Data in the top half of the figure is reproduced from ref. 23 with permission.