Peculiar features of the interaction potential between hydrogen and antihydrogen at intermediate separations

This paper evaluates the interaction potential between a hydrogen and an antihydrogen using the second-order perturbation theory within the framework of the four-body system in a separable two-body basis. It finds that the H--\bar\rm H interaction potential possesses the peculiar features of a shallow local minimum located around interatomic separations of r\sim 6 a.u. and a barrier rising at r\lesssim5 a.u.