The P-V-T Equation of State of Ni3Si

Geophysical measurements, cosmo-chemical abundances, observations of meteorites, and data from spacecraft indicate that the metallic cores of the terrestrial planets (and e.g. the Jovian moon Ganymede), must be composed of iron alloyed with nickel and with a lighter element such as silicon. Surprisingly, the physical properties of relevant materials, such as Fe3Si and Ni3Si, are not yet well known at the pressures (P) and temperatures (T) of the cores of the Moon, Mercury, Mars and Ganymede. This proposal addresses this dearth of knowledge by studying the behaviour of Ni3Si at simultaneous high pressure and temperature using the PEARL diffractometer. We shall determine both how the volume responds to P and T (the "equation of state") and the extent to which Ni and Si atoms become disordered at high T. Ni3Si is also of industrial importance as a corrosion-resistant, high-strength alloy.