Equation of state of Fe3S at room temperature up to 2 megabars

• The EOS of Fe3S was investigated up to 200 GPa at room temperature using DAC.
• The 4th Birch–Murnaghan EOS was fitted to present compression data.
• The maximum amount of S in the inner core was estimated to be 11.4(14) at.%.

The equation of state of Fe3S was investigated up to 200 GPa at room temperature using a diamond anvil cell. Fe3S adopts a tetragonal structure up to 200 GPa and no phase transition was observed. The fourth-order Birch–Murnaghan equation of state (EOS) was fitted to present compression data at room temperature. The elastic parameters, such as bulk modulus (K0), its pressure derivative (K0′), and K0″(dK′/dP) were determined to be 122.4(50) GPa, 5.36(48), and −0.066(30) GPa−1, respectively by fixing the zero pressure volume, V0, to be 377 Å3. Based on fourth-order Birch–Murnaghan EOS of Fe3S, the maximum amount of S in the inner core was estimated to be 11.4(14) at.% based on the density deficit of the inner core.