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氮的高温高压物态方程以及相图对于研究和制备高能量密度含能材料的至关重要。本文采用基于密度泛函理论的分子动力学模拟方法，研究了液氮的高温高压行为，给出900-25000 K、2-200 GPa区间流体氮的物态方程以及组分、相态变化。在上述相空间，我们观察到流体氮分子相-聚合物相以及聚合物-原子相的相变发生。获得的液氮Hugoniot理论曲线与实验结果吻合较好，发现30-60 GPa区间Hugoniot曲线的软化与分子—聚合物流体相的相变有关；在60 GPa后Hugoniot曲线变陡峭与流体氮进入聚合物相区有关。
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关键词:
- 流体氮 /
- 密度泛函分子动力学模拟 /
- 物态方程 /
- 相变 /
- 高温高压
Nitrogen is the main reaction and detonation product of energetic materials. Therefore, studying the equation of state and phase transition of nitrogen at high temperature and high pressure is very important for evaluating the energy characteristics of energetic materials, especially in the design of a new generation of nitrogen-rich energetic materials. Using density functional molecular dynamics simulation method, we calculated the pressure, internal energy and chemical components of fluid nitrogen in the range of 900-25000 K and 2-300 GPa. The negative change of pressure with temperature on isochores are observed under the temperature and pressure conditions of 3000-10000 K, 20-80 GPa. As the temperature increases, the pressure drop caused by the collapse of nitrogen molecules. This phenomenon is related to the phase transition from molecular fluid nitrogen to polymerized fluid nitrogen. The triple bond in the molecule breaks and a polymer forms which connected by single and double bonds with neighboring atom. We also studied the equation of state along Hugoniot under impact loading. The obtained Hugoniot curve is in good agreement with the experimental results. It is found that the softening of the experimental curve in the range of 30-60 GPa is related to the decomposition of nitrogen molecules of nitrogen molecules and the formation of polymeric nitrogen.-
Keywords:
- fluid nitrogen /
- molecular dynamics simulation /
- equation of state /
- phase transition /
- high pressures and temperatures
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