High-Z materials exhibit a broad range of variation of the charge state in the hot dense regime, and so ionic structures become complex with increasing density and temperature owing to ionization. Taking high-Z uranium as example, we study its electronic and ionic structures in the hot dense regime by combining an average-atom model with the hypernetted chain approximation. The electronic structure is described by solving the Dirac equation, taking account of relativistic effects, including broadening of the energy levels, and the effect of other ions via correlation functions. On the basis of the electronic distribution around a nucleus, the ion pair potential is constructed using the modified Gordon–Kim model in the frame of temperature-dependent density functional theory. Because of the presence of ion–ion strong coupling, the bridge function is included in the hypernetted chain approximation, which is used to calculate the correlation functions. To take account of the influence on transport properties of the strong correlation of electrons with highly charged ions, we perform both classical and Langevin molecular dynamics simulations to determine ion self-diffusion coefficients and the shear viscosity, using the Green–Kubo relation and an ion–ion pair potential with good convergence. We show that the influence of electron–ion collisions on transport properties becomes more important as the free electron density increases owing to thermal ionization.

中文翻译：

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热致密态下高Z材料的离子自扩散系数和剪切粘度

高Z材料在热致密态下表现出大范围的电荷状态变化，因此由于电离，离子结构随着密度和温度的升高而变得复杂。高Z以铀为例，我们通过将平均原子模型与超网状链近似相结合，研究了在热致密态下的电子和离子结构。通过解决狄拉克方程来描述电子结构，其中考虑了相对论效应，包括能级增宽，以及其他离子通过相关函数的效应。根据原子核周围的电子分布，在依赖温度的密度泛函理论的框架内，使用改进的Gordon-Kim模型构造离子对电势。由于存在离子-离子强耦合，因此在超网状链逼近中包括了桥函数，该桥函数用于计算相关函数。考虑到电子与高电荷离子的强相关性对传输性质的影响，我们使用Green-Kubo关系和一个离子执行经典和Langevin分子动力学模拟，以确定离子的自扩散系数和剪切粘度。 -离子对电位，具有良好的收敛性。我们表明，由于自由电子密度由于热电离而增加，电子离子碰撞对传输性质的影响变得更加重要。