Nguyen Jeffrey H, Holmes Neil C
Physics and Advanced Technologies, H-Division, Lawrence Livermore National Laboratory, Livermore, California 94551, USA.
Nature. 2004 Jan 22;427(6972):339-42. doi: 10.1038/nature02248.
Seismological data can yield physical properties of the Earth's core, such as its size and seismic anisotropy. A well-constrained iron phase diagram, however, is essential to determine the temperatures at core boundaries and the crystal structure of the solid inner core. To date, the iron phase diagram at high pressure has been investigated experimentally through both laser-heated diamond-anvil cell and shock-compression techniques, as well as through theoretical calculations. Despite these contributions, a consensus on the melt line or the high-pressure, high-temperature phase of iron is lacking. Here we report new and re-analysed sound velocity measurements of shock-compressed iron at Earth-core conditions. We show that melting starts at 225 +/- 3 GPa (5,100 +/- 500 K) and is complete at 260 +/- 3 GPa (6,100 +/- 500 K), both on the Hugoniot curve-the locus of shock-compressed states. This new melting pressure is lower than previously reported, and we find no evidence for a previously reported solid-solid phase transition on the Hugoniot curve near 200 GPa (ref. 16).
地震学数据能够得出地核的物理性质，比如其大小和地震各向异性。然而，一个精确的铁相图对于确定地核边界处的温度以及固态内核的晶体结构至关重要。迄今为止，高压下的铁相图已经通过激光加热金刚石压腔和冲击压缩技术以及理论计算进行了实验研究。尽管有这些研究成果，但对于铁的熔点线或高压高温相仍缺乏共识。在此，我们报告了在地核条件下对冲击压缩铁进行的新的以及重新分析的声速测量结果。我们表明，在冲击绝热线（冲击压缩状态的轨迹）上，熔化始于225±3吉帕（5100±500开尔文），并在260±3吉帕（6100±500开尔文）时完成。这个新的熔化压力低于先前报道的值，并且我们没有发现证据表明在冲击绝热线附近200吉帕处存在先前报道的固 - 固相变（参考文献16）。
