Enthalpy (here equal to Gibbs free energy) of NiSi phases from athermal VASP simulations as a function of pressure, relative to that of the CsCl structure. The enthalpy curves shown are identical to those given in Fig. 3 of Vočadlo et al. (2012), with the curve for the new Pmmn phase added (thick dot–dashed line; shown in red in the electronic version of the journal). With increasing pressure the sequence of stable phases of NiSi is now MnP structured → Pmmn phase → CsCl structured, with transition pressures of 21 and 264 GPa, respectively. Note, however, that the free-energy difference between many of the structures is only ∼5–25 meV atom−1.