Fe3C up to core conditions

We study iron carbide, Fe3C, under pressure employing state-of-the-art first-principles calculations based on the planar-augmented wavefunctions (PAW) approach to density-functional theory (DFT) in the ABINIT implementation. We investigate in large detail the magnetism of the structure, considering a variety of spin configurations and residual values, over a large pressure range. We find that the spin decreases continuously and at about 50 GPa it completely vanishes. The ferromagnetic configurations are more favorable than the antiferromagnetic or ferromagnetic ones. Next we compute the elasticity and the seismic properties up to inner core pressures and, as expected, find that carbon would considerably reduce the seismic wave velocities and density of the iron-based alloys of the Earth’s core.