The ambient-pressure Pnma phase of NiSi is a technologically important material used to form contacts in microelectronics. Recently we carried out the first study of NiSi at high pressure (Vocadlo et al., 2012; J. Appl. Cryst. 45, 186-196). Using athermal ab initio computer simulations, we predicted that NiSi will exist in five different structures for 0 < P < 300 GPa. In a parallel experimental programme, we have confirmed the existence of at least 3 of these phases, together with another that was marginally unstable in the simulations. This ISIS proposal addresses two further aspects of our investigation of NiSi: (i) the need for accurate experimental volumetric and axial equations of state of the ambient-pressure phase and (ii) the need for accurate atomic coordinates at simultaneous high pressure and temperature to allow us to validate ongoing finite temperature computer simulations.