The difference in the polyphosphate chain length between the three surfaces is much more subtle than the difference in TCP decomposition rates. This is probably because iron atoms or ions, which are most readily available in α-Fe(110), accelerate the depolymerisation of the polyphosphate chains by P-O bond cleavage. Similarly, the polyphosphate chain length does not vary significantly over the wide range of temperatures and pressures studied in the NEMD simulations, as shown in the ESI (Figure ). This is because both the polymerisation (P-O formation) and depolymerisation (P-O dissociation) reactions are accelerated by a similar amount due to increased temperature and shear stress, as shown in Figure .