The phase diagram of NiSi under the conditions of small planetary interiors
The phase diagram of NiSi under the conditions of small planetary interiors
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DOI：
10.1016/j.pepi.2016.10.005
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发表时间：
2016-12-01
影响因子：
2.3
通讯作者：
Mezouar, Mohamed
中科院分区：
文献类型：
--
作者：
Dobson, David P.;Hunt, Simon A.;Mezouar, Mohamed
使用原位同步加速器 X 射线粉末衍射多砧实验在 19 GPa 下确定了 NiSi 的相图，并在 60 GPa 下的激光加热金刚石池中得到了进一步的初步结果。低压 MnP 结构相根据温度转变为两种不同的高压相：ε-FeSi 结构在高于 1100 K 的温度下稳定，之前报道的扭曲 CuTi 结构（具有 Pmmn 对称性）在较低温度下稳定。不变点位于 12.8 +/- 0.2 GPa 和 1100 +/- 20 K。在较高压力下，ε-FeSi 结构的 NiSi 转变为 CsCl 结构，其中 CsCl-NiSi 作为液相线相，高于 30 GPa。该转变的克拉佩龙斜率是-67 MPa/K。 epsilon-FeSi 和 Pmmn 结构相之间的相界几乎与压力无关，这意味着在比本研究中获得的压力更高的压力下，CsCl、epsilon-FeSi 和 Pmmn 结构之间将存在第二个亚固相线不变点。除了这些稳定相之外，还观察到 MnP 结构在室温下自发转变为新的斜方结构（也具有 Pnma 对称性），这在之前的从头算模拟中已详细介绍。此处显示的 NiSi 新相是亚稳态的。 (C) 2016 年作者。由 Elsevier B.V. 出版
The phase diagram of NiSi has been determined using in situ synchrotron X-ray powder diffraction multi anvil experiments to 19 GPa, with further preliminary results in the laser-heated diamond cell reported to 60 GPa. The low-pressure MnP-structured phase transforms to two different high-pressure phases depending on the temperature: the epsilon-FeSi structure is stable at temperatures above similar to 1100 K and a previously reported distorted-CuTi structure (with Pmmn symmetry) is stable at lower temperature. The invariant point is located at 12.8 +/- 0.2 GPa and 1100 +/- 20 K. At higher pressures, epsilon-FeSi-structured NiSi transforms to the CsCl structure with CsCl-NiSi as the liquidus phase above 30 GPa. The Clapeyron slope of this transition is -67 MPa/K. The phase boundary between the epsilon-FeSi and Pmmn structured phases is nearly pressure independent implying there will be a second sub-solidus invariant point between CsCl, epsilon-FeSi and Pmmn structures at higher pressure than attained in this study. In addition to these stable phases, the MnP structure was observed to spontaneously transform at room temperature to a new orthorhombic structure (also with Pnma symmetry) which had been detailed in previous ab initio simulations. This new phase of NiSi is shown here to be metastable. (C) 2016 The Authors. Published by Elsevier B.V.