Melting and dissociation of ammonia at high pressure and high temperature
Melting and dissociation of ammonia at high pressure and high temperature
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DOI：
10.1063/1.4742340
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发表时间：
2012-08-14
影响因子：
4.4
通讯作者：
Goncharov, Alexander F.
中科院分区：
文献类型：
--
作者：
Ojwang, J. G. O.;McWilliams, R. Stewart;Goncharov, Alexander F.
拉曼光谱和同步辐射X射线衍射测量氨（NH3）在激光加热的金刚石对顶砧单元，在压力高达60 GPa和温度高达2500 K，揭示了熔化线表现出最大值接近37 GPa和分子间质子波动大幅增加的流体中的压力。我们发现NH3在高压下是化学不稳定的，部分解离成N-2和H-2。在这项工作中进行的从头计算表明，这一过程是热力学驱动的。化学反应性在高温下（在T > 1700 K的流体相中）显著增加，几乎与压力无关。从这些高温条件淬火，NH3表现出与已知固相的结构差异。我们认为，NH3的化学反应性与理论预测的动态解离和电离的竞争。(C)2012年美国物理学会。[http：//dx.doi.org/10.1063/1.4742340]
Raman spectroscopy and synchrotron x-ray diffraction measurements of ammonia (NH3) in laser-heated diamond anvil cells, at pressures up to 60 GPa and temperatures up to 2500 K, reveal that the melting line exhibits a maximum near 37 GPa and intermolecular proton fluctuations substantially increase in the fluid with pressure. We find that NH3 is chemically unstable at high pressures, partially dissociating into N-2 and H-2. Ab initio calculations performed in this work show that this process is thermodynamically driven. The chemical reactivity dramatically increases at high temperature (in the fluid phase at T > 1700 K) almost independent of pressure. Quenched from these high temperature conditions, NH3 exhibits structural differences from known solid phases. We argue that chemical reactivity of NH3 competes with the theoretically predicted dynamic dissociation and ionization. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4742340]