QCDark 2.0: Computing the dielectric function for light dark matter direct detection and beyond

Direct detection experiments for light dark matter require the accurate computation of the detector material's dielectric function to account for in-medium screening effects. Software developed for condensed matter applications are inadequate because the dielectric function must be calculated for wide ranges of transferred momentum and energy. Existing direct detection codes such as QEDark, QCDark, DarkELF, and EXCEED-DM have trade-offs between computational cost and accuracy of the dielectric function. We will present the methodology and selected results of our improved python-based code QCDark 2.0 which calculates the dielectric function using the random phase approximation. Atom-centered Gaussian-type orbitals, all-electron density functional theory, local field effects, and interpolation are employed to obtain good accuracy over the entire relevant momentum range.