Short-range screening potentials for classical Coulomb fluids: Monte Carlo sampling and cluster model studies

Screening potential, the balance between the bare Coulomb repulsion and the potential of mean force in a charged liquid, plays an essential role in the theoretical estimation of enhancement for the nuclear reaction rates in dense stellar matter. For the accurate assessment of the screening potential at short interparticle separations, we revisit the first-principles calculations for the coefficients of the Widom expansion and undertake extra-long Monte Carlo samplings in specifically designed binary-ionic systems. The results are compared with those obtained from an approximate estimation based on extrapolation from intermediate distances. We also present model calculations of the screening potential with two-ion clusters, which shed light on the relation between the short- and intermediate-range behaviors.