Reply to "Comment on 'Dispersion Interaction between Two Hydrogen Atoms in a Static Electric Field' "

In their Comment on our Letter Dispersion Interaction between Two Hydrogen Atoms in a Static Electric Field, P. P. Abrantes et al. address one of the main points discussed in our Letter, that is, the possibility to manipulate interatomic interactions through an external static electric field. In our Letter, we have shown that the interaction between two ground-state atoms can be significantly modified, exploiting an external static electric field, and even turned from attractive to repulsive, depending on the strength of the external field and the geometrical configu- ration. In their Comment, Abrantes et al. point out that it is the electrostatic contribution between the electric dipoles induced in both atoms by the external field that is dominant and can become repulsive, overcoming the usual attractive dispersion force. They write the interatomic force as the sum of a classical electrostatic dipole-dipole interaction and a dispersion interaction modified by the external field and point out that it is the total force that changes its sign. As we discuss below in more detail, we partially agree with their interpretation of this result. Essential points, in our opinion, are the exact definition of the dispersion interaction and how it is separated from the (classical) electrostatic con- tribution when the atoms are polarized by the static electric field, clarifying which quantity is evaluated at any step.