Abstract Dense bulk Fe3C samples were synthesized by the high pressure–temperature method using a large-volume cubic press. The Hugoniot data of the Fe3C samples were measured from 65 to 250 GPa on a two-stage light gas gun. The shock velocities were measured by the electrical pin technique, and the particle velocities were calculated by the impedance match method. The shock velocity (Us) and particle velocity (Up) relationship of Fe3C was determined to be linear and described by Us = 4.77(7) + 1.60(2) Up. The thermal contributions of electronics and lattices were determined by first-principle simulation and thermodynamic calculation, respectively. Subsequently, the thermal equation of state of Fe3C was used to constrain the carbon amount in the inner core. We conclude that 2.9 ± 0.4 wt% carbon is needed to compensate for the density deficit between pure iron and the inner core, if carbon is the sole light element present in the core.

中文翻译：

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高达 250 GPa 的渗碳体 (Fe3C) 状态 Hugoniot 方程及其地球物理意义

摘要 使用大体积立方压机通过高压-温度法合成了致密块状 Fe3C 样品。Fe3C 样品的 Hugoniot 数据是在两级轻气枪上从 65 到 250 GPa 测量的。冲击速度采用电针技术测量，粒子速度采用阻抗匹配法计算。Fe3C 的冲击速度 (Us) 和粒子速度 (Up) 关系被确定为线性关系，并由 Us = 4.77(7) + 1.60(2) Up 描述。电子学和晶格的热贡献分别由第一性原理模拟和热力学计算确定。随后，利用 Fe3C 的热态方程来约束内核中的碳量。我们得出的结论是 2.9 ± 0。