Dissociation of methane under high pressure
Dissociation of methane under high pressure
复制标题
甲烷在高压下分解
DOI：
10.1063/1.3488102
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发表时间：
2010-10-14
影响因子：
4.4
通讯作者：
Zou, Guangtian
中科院分区：
文献类型：
--
作者：
Gao, Guoying;Oganov, Artem R.;Zou, Guangtian
甲烷是一种极其重要的能源，在自然界中含量丰富，在行星物理学中起着重要作用，是巨型行星天王星和海王星的主要成分之一。甲烷在极端条件下的稳定晶体形式具有很大的根本意义。利用从头算进化算法预测晶体结构，我们发现了三种新的绝缘分子结构，空间群分别为P2（1）2（1）2（1），Pnma和Cmcm。值得注意的是，在高压下，甲烷变得不稳定，并且在95 GPa下解离成乙烷（C（2）H（6）），在158 GPa下解离成丁烷（C（4）H（10）），并且在零温度下在287 GPa以上进一步解离成碳（金刚石）和氢。我们已经计算出的压力-温度相图，揭示了看似矛盾的观察异常低的形成压力的金刚石在高温下和实验观察的失败在室温下的解离。我们的研究结果支持在海王星等巨行星内部形成钻石的想法。(C)2010年美国物理学会。[doi：10.1063/1.3488102]
Methane is an extremely important energy source with a great abundance in nature and plays a significant role in planetary physics, being one of the major constituents of giant planets Uranus and Neptune. The stable crystal forms of methane under extreme conditions are of great fundamental interest. Using the ab initio evolutionary algorithm for crystal structure prediction, we found three novel insulating molecular structures with P2(1)2(1)2(1), Pnma, and Cmcm space groups. Remarkably, under high pressure, methane becomes unstable and dissociates into ethane (C(2)H(6)) at 95 GPa, butane (C(4)H(10)) at 158 GPa, and further, carbon (diamond) and hydrogen above 287 GPa at zero temperature. We have computed the pressure-temperature phase diagram, which sheds light into the seemingly conflicting observations of the unusually low formation pressure of diamond at high temperature and the failure of experimental observation of dissociation at room temperature. Our results support the idea of diamond formation in the interiors of giant planets such as Neptune. (C) 2010 American Institute of Physics. [doi:10.1063/1.3488102]