内地核中碳含量的第一性原理研究

Carbon amount of Earth’s inner core by first-principles study

基于第一性原理GGA-PBE方法计算了零温下Fe_(3) C的状态方程和声速.使用半经验方法确定了Fe_(3) C在高压下的晶格和电子格林爱森(Grüneison)参数.将Fe_(3) C的0-K等温线外推至内地核条件,发现需要3.1wt%碳才能解释内地核的密度亏损问题.计算出的Fe_(3) C的纵波声速(Vp)高于纯铁,且横波声速(Vs)与纯铁相当,表明碳不是内地核中主要的轻元素.

The equation of state and sound velocity of Fe_(3) C at zero Kelvin are calculated by the first principles method within the GGA-PBE (generalized gradient approximation ) framework. The lattice and electronic Grüneison parameters of Fe_(3) C at high pressure are determined with semi-empirical methods. Extrapolating the 0-K isothermal of Fe_(3) C to the Earth’s inner core conditions suggests that 3.1 wt% carbon is needed to account for the density deficit between pure iron and the inner core. The calculated longitudinal velocity ( V p ) of Fe_(3) C is higher than pure iron and shear velocity ( V s ) is comparable to pure iron, suggesting that carbon is not a major light element in earth’s inner core.