The dipole moment matrix at each R is diagonal in this diabatic representation. This is because the diabatic states |I⟩ and |C⟩, so-called Mulliken-Hush diabatic states, are the eigenstates of the electronic transition dipole operator by definition (see discussion around Eq.29). Fig. presents the matrix elements of μ in both the diabatic (solid lines) and the adiabatic (dashed lines) representations. As expected, the permanent dipole for the ionic state |I⟩ (corresponding to Li + F -) µ I (R) linearly increases, while the permanent dipole for the |C⟩ state (corresponding to covalently bonded Li-F ) µ C (R) remains nearly zero with increase in inter-atomic separation R. The adiabatic states switch their characters around R ≈ 13.5 a.u., as a result, the adiabatic permanent dipole switches in that region, and µ eg (R) peaks at R ≈ 13.5 a.u.