Dispersion coefficients for interactions between positronium and light atoms with pure Coulomb and screened Coulomb potentials

The Van der Waals two-body dispersion coefficients for interactions between the positronium (Ps) atom and light atoms have been investigated using highly correlated exponential basis functions in the framework of both pure Coulomb and screened Coulomb potentials. The C6, C8 and C10 coefficients for Ps–Ps and Ps–H interactions, and the C6 coefficients for Ps–He interactions for both the screened and unscreened cases, are reported.