Liu Hao, Zhang Yin, Kang Wei, Zhang Ping, Duan Huiling, He X T
HEDPS, Center for Applied Physics and Technology, College of Engineering, Peking University, Beijing 100871, China.
Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China.
Phys Rev E. 2017 Feb;95(2-1):023201. doi: 10.1103/PhysRevE.95.023201. Epub 2017 Feb 1.
We present a molecular dynamics simulation of shock waves propagating in dense deuterium with the electron force field method [J. T. Su and W. A. Goddard, Phys. Rev. Lett. 99, 185003 (2007)PRLTAO0031-900710.1103/PhysRevLett.99.185003], which explicitly takes the excitation of electrons into consideration. Nonequilibrium features associated with the excitation of electrons are systematically investigated. We show that chemical bonds in D_{2} molecules lead to a more complicated shock wave structure near the shock front, compared with the results of classical molecular dynamics simulation. Charge separation can bring about accumulation of net charges on large scales, instead of the formation of a localized dipole layer, which might cause extra energy for the shock wave to propagate. In addition, the simulations also display that molecular dissociation at the shock front is the major factor that accounts for the "bump" structure in the principal Hugoniot. These results could help to build a more realistic picture of shock wave propagation in fuel materials commonly used in the inertial confinement fusion.
我们采用电子力场方法[J. T. 苏和W. A. 戈达德,《物理评论快报》99, 185003 (2007年) PRLTAO0031 - 900710.1103/PhysRevLett.99.185003]对冲击波在高密度氘中的传播进行了分子动力学模拟,该方法明确考虑了电子的激发。系统地研究了与电子激发相关的非平衡特征。我们表明,与经典分子动力学模拟结果相比,D₂分子中的化学键在激波前沿附近导致了更复杂的冲击波结构。电荷分离会导致大尺度上净电荷的积累,而不是形成局部偶极层,这可能会给冲击波传播带来额外能量。此外,模拟还显示,激波前沿的分子解离是导致主雨贡纽曲线中“凸起”结构的主要因素。这些结果有助于构建惯性约束聚变中常用燃料材料中冲击波传播的更真实图像。