Elastic properties of iron-rich hcp Fe–Mg alloys up to Earth's core pressures

Abstract

Using density functional theory formulated within the framework of the exact muffin-tin orbital method, we investigate the elastic properties of hexagonal closed-packed Fe–Mg alloys, containing 5 and 10 at.% Mg, up to pressures of the Earth's inner core. We demonstrate the effect of Mg alloying on the hexagonal axial ratio, elastic constants, density and sound wave velocities. We find that 10% Mg alloying decreases the shear modulus of iron by 23% and reduces the transverse sound velocity, v S by 12% at core pressures. Although it is debated whether or not Mg can partition into the core, our results support Mg as a candidate light element in the core.