Hydrogen-antihydrogen interaction: spectacular breakdown of the adiabatic approximation

The adiabatic correction for the hydro-antihydrogen interaction in the ground state has been calculated using the Born-Handy method. The variational wavefunction was a Linear combination of explicitly correlated Gaussian functions. It has been found that the correction grows rapidly for the nuclear separation approaching the critical distance. It is hypothesized that it becomes infinite at the point where the bound-state solution of the leptonic Schrodinger equation with fixed nuclei changes to a continuum wavefunction. This effect is nonphysical and means that there is no reasonable way to extend the adiabatic ground-state potential energy curve below the critical distance in a strict manner.