Structural and transport properties of ammonia along the principal Hugoniot.
Structural and transport properties of ammonia along the principal Hugoniot.
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氨沿主雨格尼奥的结构和输运特性。
DOI：
10.1038/s41598-017-12429-w
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发表时间：
2017-09-26
影响因子：
4.6
通讯作者：
Zhang P
中科院分区：
文献类型：
--
作者：
Li D;Wang C;Yan J;Fu ZG;Zhang P
我们调查，通过量子分子动力学模拟，氨沿着主要Hugoniot的结构和输运性质的温度高达10 eV和密度高达2.6 g/cm 3。利用键自相关函数对分子动力学轨迹进行分析，确定了氨的局部化学结构的三个不同的压力-温度区域。通过拟合速度和应力张量自相关函数，得到了包含结构和多时间尺度的复杂函数形式，得到了高精度的强关联氨的扩散系数和粘滞系数。对输运性质的统计误差进行了估计。结果表明，在这三个政权的扩散率和粘度表现在一个明显不同的方式，从而呈现复杂的功能。在分子流体区域，氢原子具有与氮原子几乎相似的扩散率，并且粘度由动力学贡献主导。当进入混合区时，由于离子耦合的增强，体系的输运行为发生了显著变化，在Hugoniot上测得体系的粘度逐渐降低，在2.0 g/cm 3左右达到最小值。在等离子体状态下，氢原子的扩散速度至少是氮原子的两倍。
We investigate, via quantum molecular dynamics simulations, the structural and transport properties of ammonia along the principal Hugoniot for temperatures up to 10 eV and densities up to 2.6 g/cm3. With the analysis of the molecular dynamics trajectories by use of the bond auto-correlation function, we identify three distinct pressure-temperature regions for local chemical structures of ammonia. We derive the diffusivity and viscosity of strong correlated ammonia with high accuracy through fitting the velocity and stress-tensor autocorrelation functions with complex functional form which includes structures and multiple time scales. The statistical error of the transport properties is estimated. It is shown that the diffusivity and viscosity behave in a distinctly different manner at these three regimes and thus present complex features. In the molecular fluid regime, the hydrogen atoms have almost the similar diffusivity as nitrogen and the viscosity is dominated by the kinetic contribution. When entering into the mixture regime, the transport behavior of the system remarkably changes due to the stronger ionic coupling, and the viscosity is determined to decrease gradually and achieve minimum at about 2.0 g/cm3on the Hugoniot. In the plasma regime, the hydrogen atoms diffuse at least twice as fast as the nitrogen atoms.
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