Dissociation timescale for circumcircumcoronene clusters in the T Tauri model. Solid lines: MC simulations. Crosses: statistical calculations. Circles: value at radiative equilibrium temperature. The transition from green to black denotes the cluster size at which the vertical mixing timescale equals the dissociation timescale. Up to 0.9 AU, the radiative equilibrium temperature is higher than the critical temperature for dissociation and cluster cannot gain stability. At larger distances, cluster stability increases with a few more cluster member.