The 5 kJ mol -1 increments in threshold energy limit the precision with which the energy barrier between the two polymorphs can be estimated. Knowing that the transi- tion occurs when the threshold is 15 kJ mol -1 or less above polymorph B, we re-sampled the landscape in space group P 2 1 /c (four molecules in the unit cell), with smaller threshold increments of 1 kJ mol -1 and 1,000 steps under each lid energy (a five-fold increase in sampling per unit increase in the lid energy). Again, simulations were started from both polymorphs, for 15 increases in the lid energy. With this increased sampling, the energy barrier is now located when the threshold is 10 kJ mol -1 above polymorph B, 6 kJ mol -1 above A, and no other local energy minima are visited up to the highest energy threshold.