Figure in the Supplementary Information illustrates a typical temperature profile along the z-axis for the PAO4 systems during the NEMD simulation. The system was divided into 200 bins along the z-axis and each point on the graph represents the temperature of one bin, averaged over the final 5 ns of the NEMD simulation. ∇T was calculated by linear fitting a 10 Å region in the centre of the hot and cold thermostats to avoid fitting the non-linear regions of the temperature profile near the thermostats. ∇T was taken as the average of the two fitted regions. The energies exchanged in the hot and cold thermostats during the simulation are shown by the red and blue lines respectively in Figure in the Supplementary