Equation (2) contains a typographical error. The correct equation is

Vij(2)(r)=Hijrηij+ZiZjrer/λDij2r4er/ξWijr6.
(2)

Note that it does not affect any results in the paper.

The authors are grateful to N. Tymiak, D. Chrobak, S. Nagao, K. Nordlund, J. Räisänen, W. Gerberich, and R. Nowak, who brought the error to our attention.