Phase Transition and Chemical Decomposition of Liquid Oxygen and Nitrogen Mixture under High Pressures

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• 作者：XiaoXu Jiang ; GuanYu Chen ; XinLu Cheng ; YuTong Li ; Feng Guo
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：June 30, 2016
• 年：2016
• 卷：120
• 期：25
• 页码：13366-13374
• 全文大小：759K
• 年卷期：0
• ISSN：1932-7455

文摘

The thermophysical properties of the liquid oxygen and nitrogen (O₂–N₂) mixture under extreme conditions are studied by quantum molecular dynamic (QMD) simulations based on van der Waals (vdW) density-functional theory (DFT-D). We have calculated the principal Hugoniots of the O₂–N₂ mixture both with and without explicit treatment of spin, and obtained good agreement with shock experiments along the first shock Hugoniot. The Hugoniot is not significantly sensitive to the spin effects, while the key role of spin effect on the structural properties is found. When density and pressure increase, the O₂–N₂ mixture is observed to undergo a continuous transition. The dissociation, recombination of N₂ and O₂ molecules, and formation of products, such as NO, NO₂, NO₃, and N₂O, along the Hugoniot have been predicted by means of pair-correlation functions (PCFs), and the configuration evolution of the system is also discussed. We find the decomposition of N₂ molecules occurs at much a lower temperature and pressure (4000 K, 19 GPa) than those for pure liquid nitrogen. With the continuous increase of density and temperature, the formation of polymeric structures is observed. To study the Mott transition, we calculate the electronic density of states (DOS) of the O₂–N₂ mixture along the 500 K isotherm and the transformation from a semiconducting to a metallic fluid occurs at the pressure approaching 36 GPa, where the liquid mixture consists entirely of stable molecules.