Dynamic Ion Structure Factor of Warm Dense Matter

The dynamics of the ion structure in warm dense matter is determined by molecular dynamics simulations using an effective ion-ion potential. This potential is obtained from ab initio simulations and has a strong short-range repulsion added to a screened Coulomb potential. Models based on static or dynamic local field corrections are found to be insufficient to describe the data. An extended Mermin approach, a hydrodynamic model, and the method of moments with local constraints are capable of reproducing the numerical results but have rather limited predictive powers as they all need some numerical data as input. The method of moments is found to be the most promising.

Figure 1

DISF for the effective ion-ion potential (1) compared to the one for a Yukawa system. Both results are obtained by MD for the example of shocked silicon [19].

Figure 2

DISF obtained with MD simulations and from theories applying different LFCs for the effective potential (1) and a wave number $kd=0.2455$. Bottom panel: LFC entering the calculations for the respective DISF.

Figure 3

Dispersion relation of the ion acoustic mode obtained from MD and different LFC theories applying the potential (1). The FWHM of the ion acoustic peaks are indicated by error bars for the MD data. The ratio of FWHMs from LFC and MD are given separately.

Figure 4

DISF of the $\mathrm{\text{Yukawa}}+\mathrm{\text{SRR}}$ system for four different wave vectors in different approximations: MD (black line with dots), Mermin $+G(k,0)$ (blue, short dashed line), hydrodynamic model (green, long dashed line), method of moments with one local constraint (red, dash-dotted line), and method of moments with the static Nevanlinna function (brown, dotted line).