Hu S X, Boehly T R, Collins L A
Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623, USA.
Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Jun;89(6):063104. doi: 10.1103/PhysRevE.89.063104. Epub 2014 Jun 30.
Polystyrene (CH) is often chosen as the ablator material for inertial confinement fusion (ICF) targets. Its static, dynamical, and optical properties in warm, dense conditions (due to shock compression) are important for ICF designs. Using the first-principles quantum molecular dynamics (QMD) method, we have investigated the equation of state (EOS) and optical reflectivity of shock-compressed CH up to an unprecedentedly high pressure of 62 Mbar along the principal Hugoniot. The QMD results are compared with existing experimental measurements as well as the SESAME EOS model. Although the Hugoniot pressure and/or temperature from QMD calculations agrees with experiments and the SESAME EOS model at low pressures below 10 Mbar, we have identified for the first time a stiffer behavior of shocked CH at higher pressures (>10 Mbar). Such a stiffer behavior of warm, dense CH can affect the ablation pressure (shock strength), shock coalescence dynamics, and nonuniformity growth in ICF implosions. In addition, we corrected the mistake made in literature for calculating the reflectivity of shocked CH and obtained good agreements with experimental measurements, which should lend credence to future opacity calculations in a first-principles fashion.
聚苯乙烯（CH）常被选作惯性约束聚变（ICF）靶丸的烧蚀材料。其在温暖、高密度条件下（由于冲击压缩）的静态、动态和光学性质对ICF设计至关重要。利用第一性原理量子分子动力学（QMD）方法，我们沿着主雨贡纽研究了冲击压缩CH在高达62兆巴这一前所未有的高压下的状态方程（EOS）和光学反射率。将QMD结果与现有的实验测量结果以及SESAME EOS模型进行了比较。尽管在低于10兆巴的低压下，QMD计算得到的雨贡纽压力和/或温度与实验以及SESAME EOS模型相符，但我们首次发现，在更高压力（>10兆巴）下，冲击压缩CH表现出更硬的特性。温暖、高密度CH的这种更硬特性会影响ICF内爆中的烧蚀压力（冲击强度）、冲击合并动力学以及不均匀性增长。此外，我们纠正了文献中在计算冲击压缩CH反射率时所犯的错误，并与实验测量结果取得了良好的一致性，这应为未来以第一性原理方式进行的不透明度计算提供可信度。
