Density measurement of Fe3C liquid using X-ray absorption image up to 10 GPa and effect of light elements on compressibility of liquid iron

Density of liquid iron alloy under high pressure is important to constrain the amount of light elements in the Earth's core. Density measurement of solid and liquid Fe3C was performed using X-ray absorption image technique up to 9.5 GPa and 1973 K. Density of liquid Fe3C increases from 6.94 g/cm(3) to 7.38 g/cm(3) with a pressure of 3.6-9.5 GPa at 1973 K. The bulk modulus of liquid Fe3C is obtained to be 50 +/- 7 GPa at 1973 K. The effect of carbon on the compressibility of liquid iron is similar to that of sulfur, which significantly decreases the bulk modulus of liquid iron. Since carbon dissolution into liquid iron causes reduction of rho and K-0T, carbon could be excluded from the candidates of alloying light elements in the Earth's outer core.