Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory
Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory
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DOI：
10.1073/pnas.0510489103
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发表时间：
2006-01-31
影响因子：
11.1
通讯作者：
Galli, G
中科院分区：
文献类型：
--
作者：
Correa, AA;Bonev, SA;Galli, G
在高压和高温下，元素碳的相图鲜为人知。根据第一性原理计算，我们预测了金刚石和BC8在固相中的熔融线和它们的相界。在两条熔化线上都存在极大值，三重点分别位于约850 GPa和约7400K。我们的结果表明，热的、压缩的钻石是一种半导体，在熔化时经历金属化。相反，在BC8的稳定范围内，绝缘体到金属的转变很可能发生在固相中。在钻石/液体和BC8/液体边界附近，熔融碳是一种低配位金属，在极端压力下的结合中保留了一些共价特征。我们的结果提供了对碳状态方程的约束，该状态方程对于设计海王星、天王星和白矮星以及太阳系外富碳行星的模型至关重要。
At high pressure and temperature, the phase diagram of elemental carbon is poorly known. We present predictions of diamond and BC8 melting lines and their phase boundary in the solid phase, as obtained from first-principles calculations. Maxima are found in both melting lines, with a triple point located at approximate to 850 GPa and approximate to 7,400 K. Our results show that hot, compressed diamond is a semiconductor that undergoes metalization upon melting. In contrast, in the stability range of BC8, an insulator to metal transition is likely to occur in the solid phase. Close to the diamond/liquid and BC8/liquid boundaries, molten carbon is a low-coordinated metal retaining some covalent character in its bonding up to extreme pressures. Our results provide constraints on the carbon equation of state, which is of critical importance for devising models of Neptune, Uranus, and white dwarf stars, as well as of extrasolar carbon-rich planets.