The melting curve of Ni to 1 Mbar
The melting curve of Ni to 1 Mbar
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DOI：
10.1016/j.epsl.2014.09.046
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发表时间：
2014-12
影响因子：
5.3
通讯作者：
Oliver Thomas Lord;I. Wood;D. Dobson;L. Vočadlo;Weiwei Wang;A. Thomson;E. T. Wann;G. Morard;M. Mezouar;M. Walter
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文献类型：
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作者：
Oliver Thomas Lord;I. Wood;D. Dobson;L. Vočadlo;Weiwei Wang;A. Thomson;E. T. Wann;G. Morard;M. Mezouar;M. Walter
用激光加热金刚石顶锤(LHDAC)实验测定了镍的熔化曲线，实验中采用了两种熔化准则：一是在原位X射线衍射(XRD)过程中出现的液体扩散散射(LDS)；二是在原位和离线实验中的平台温度与激光功率的函数关系。我们的新熔化曲线由Simon-Glatzel定义，符合TM(K)=[(PM18.78±10.20+1)]1/2.42±0.66×1726的数据，与大多数关于Ni熔化的理论研究相一致，并与现有的冲击波熔化数据很好地吻合。然而，它比以前离线的LH-DAC研究要陡峭得多，在以前的研究中，熔化的确定是基于激光散斑方法辅助的运动的视觉观察。我们估算出Ni在330 Gpa核内边界压力下的熔点(Tm)为Tm=5800±700K(2σ)，与最近一次原位LHDAC研究中测得的Tm=6230±500K的值有一定误差。这一相似性表明，5-10wt.%Ni与富Fe核合金的合金化不太可能对ICB的温度产生任何显著影响，尽管这取决于核压下Fe-Ni二元相图的拓扑细节。在330 GPa时，Ni的熔化温度比以前用激光散斑方法得到的实验结果高出∼2500K。我们发现，这些早期的熔化曲线与快速亚固相线再结晶的开始相吻合，这表明对运动的目测可能将动态再结晶误解为熔体的对流运动。这一发现对我们理解其他一些过渡金属的高压熔化行为具有重要意义。
The melting curve of Ni has been determined to 125 GPa using laser-heated diamond anvil cell (LH-DAC) experiments in which two melting criteria were used: firstly, the appearance of liquid diffuse scattering (LDS) during in situ X-ray diffraction (XRD) and secondly, plateaux in temperature vs. laser power functions in both in situ and off-line experiments. Our new melting curve, defined by a Simon–Glatzel fit to the data where T M (K)=[(P M 18.78±10.20+ 1)] 1/2.42±0.66× 1726, is in good agreement with the majority of the theoretical studies on Ni melting and matches closely the available shock wave melting data. It is however dramatically steeper than the previous off-line LH-DAC studies in which determination of melting was based on the visual observation of motion aided by the laser speckle method. We estimate the melting point (T M) of Ni at the inner-core boundary (ICB) pressure of 330 GPa to be T M= 5800±700 K (2 σ), within error of the value for Fe of T M= 6230±500 K determined in a recent in situ LH-DAC study by similar methods to those employed here. This similarity suggests that the alloying of 5–10 wt.% Ni with the Fe-rich core alloy is unlikely to have any significant effect on the temperature of the ICB, though this is dependent on the details of the topology of the Fe–Ni binary phase diagram at core pressures. Our melting temperature for Ni at 330 GPa is∼ 2500 K higher than that found in previous experimental studies employing the laser speckle method. We find that those earlier melting curves coincide with the onset of rapid sub-solidus recrystallization, suggesting that visual observations of motion may have misinterpreted dynamic recrystallization as convective motion of a melt. This finding has significant implications for our understanding of the high-pressure melting behaviour of a number of other transition metals.