Effects of electron-ion collisions on stopping powers in warm dense matter

Collisions between electrons and ions affect the response of high energy density (HED) plasmas to external perturbations, governing transport properties such as conductivities and stopping powers. Here, we present stopping power calculations based on a collisionless random phase approximation to a warm, dense plasma, and extend this picture by including electron-ion collision frequencies calculated using an average atom code. Moreover, we show that going beyond a simple Born description of collisions by using T-matrix cross sections further modifies stopping powers in the temperature and density regimes relevant to warm dense matter (WDM). We compare these results with Ehrenfest time-dependent density functional theory (TDDFT), which extracts stopping powers directly from electron-ion dynamics, and show that the inclusion of T-matrix collisions improves agreement with TDDFT. Our simplified atomic model provides a relatively computationally inexpensive and accurate approach to computing various atomic-scale quantities of interest to the HED and astrophysical communities.