Numerical Simulation for generation of Carbon Simple Cubic by Dynamic Compression of flyer impact

研究结果表明，在激光烧蚀压力的作用下，靶与飞片的碰撞过程中，靶与飞片之间的冲击力被动态压缩，从而产生碳立方结构。预计在2Tpa以上的压力下会出现简单立方碳，但在1000K以上的温度下可能会熔化。提出了一种从金刚石开始实现低熵动态压缩的层状结构平板靶与飞片碰撞方案。利用一维拉格朗日流体动力学程序和状态方程库SEARCH研究了金刚石在压缩过程中的热力学状态。使用冲击阻抗小的材料作为冲击界面会显著降低主冲击波的强度。结果发现，冲击阻抗的梯度横跨飞片的厚度产生小的多个冲击波进入金刚石和有效的低熵压缩。得到了碳简立方低熵动态压缩所需的热力学条件。

This research numerically makes it clear that Carbon Simple Cubic is able to be generated thermodynamically by the dynamic compression of the impact at the collision between the target and flyer which is accelerated by the laser ablation pressure. The Carbon Simple Cubic is expected to appear at the pressure more than 2 Tpa, however it may melt with the temperature of more than several 1000 K. An impact scheme of a slab target and flyer with a layered structure is proposed to achieve low-entropy dynamic compression starting from diamond. The thermodynamic state of diamond during compression is examined using one-dimensional Lagrangian hydrodynamic code and the tabulated equation of state library SESAME. The use of a material with a small shock impedance for the impact interfaces markedly decreases the strength of the primary shock wave. It is found that a gradient of shock impedance across the thickness of the flyer generates small multiple shock waves into the diamond and effective for low-entropy compression. The thermodynamic conditions required for Carbon Simple Cubic and low-entropy dynamic compression is achived.