P-V- T Equations of State for Iron Carbides Fe_3C and Fe_7C_3 and Their Relationships under the Conditions of the Earth's Mantle and Core

摘要

According to the geophysical data, the outer liquid core of the Earth has a deficiency of density and seismic velocities of 5-12%, and inner solid core has 3- 5% at the expense of the presence of one or several light elements. The most probable candidates for the role of the light element are H, C, O, S, and Si. The problem of light elements may be solved using detailed thermodynamic description of solid iron and nickel compounds, as well as metal alloys, on the basis of the data on their equations of state and phase transition boundaries. The Fe-C system is of key importance for discussion of the composition of the Earth's core. The equations of state of iron carbides at 300 K are studied at pressures up to 180 GPa.