Ionic self-diffusion coefficient and shear viscosity of high-Z materials in the hot dense regime

High-Zmaterials exhibit a broad range of variation of the charge state in the hot dense regime,and so ionic structures becomecomplexwith 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-atommodelwith the hypernetted chain approximation.The electronic structure is described by solving theDirac 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 temperaturedependent density functional theory.Because of the presence of ion–ion strong coupling,the bridge function is included in the hypernetted chain approximation,whichis usedto calculate the correlation functions.To take account of the influenceon transportpropertiesof 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 theGreen–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.