Pereira Kimberly A, Clarke Samantha M, Singh Saransh, Briggs Richard, McGuire Christopher P, Lee Hae Ja, Khaghani Dimitri, Nagler Bob, Galtier Eric, Cunningham Eric, McGonegle David, Tracy Sally J, Vennari Cara, Gorman Martin G, Coleman Amy L, Davis Carol, Hutchinson Trevor, Eggert Jon H, Smith Raymond F, Walsh James P S
Department of Chemistry, University of Massachusetts Amherst, Amherst, MA, USA.
Lawrence Livermore National Laboratory, Livermore, CA, USA.
Nat Commun. 2025 May 12;16(1):4385. doi: 10.1038/s41467-025-59385-y.
Despite making up 5-20 wt.% of Earth's predominantly iron core, the melting properties of elemental nickel at core conditions remain poorly understood, due largely to a dearth of experimental data. We present here an in situ X-ray diffraction study performed on laser shock-compressed samples of bulk nickel, reaching pressures up to ~ 500 GPa. Hugoniot states of nickel were targeted using a flat-top laser drive, with in situ X-ray diffraction data collected using the Linac Coherent Light Source. Rietveld methods were used to determine the densities of the shocked states from the measured diffraction data, while peak pressures were determined using a combination of measured particle velocities, shock transit times, hydrodynamic simulations, and laser intensity calibrations. We observed solid compressed face-centered cubic (fcc) Ni up to at least 332 ± 30 GPa along the Hugoniot-significantly higher than expected from the majority of melt lines that have been proposed for nickel. We also bracket the partial melting onset to between 377 ± 38 GPa and 486 ± 35 GPa.
尽管镍元素在地球主要由铁构成的地核中占5%-20%（重量），但在核条件下元素镍的熔化特性仍知之甚少，这主要是由于缺乏实验数据。我们在此展示了一项对块状镍的激光冲击压缩样品进行的原位X射线衍射研究，压力高达约500吉帕。使用平顶激光驱动来确定镍的雨贡纽状态，并利用直线加速器相干光源收集原位X射线衍射数据。利用Rietveld方法从测量的衍射数据中确定冲击状态的密度，而峰值压力则通过测量粒子速度、冲击渡越时间、流体动力学模拟和激光强度校准相结合的方式来确定。我们观察到沿着雨贡纽曲线，固态压缩的面心立方（fcc）镍至少在332±30吉帕时仍保持固态——这比大多数已提出的镍的熔化线所预期的要高得多。我们还确定了部分熔化开始的压力范围在377±38吉帕至486±35吉帕之间。
