We would like to thank the reviewers for their carefull reading of our manuscript, and we reply in the present document to their remarks and criticisms.
This is a very high-quality manuscript, in which a DFT-based correction for finite basis-set errors in wavefunction theory is extended to the case of strongly correlated molecular systems, by looking at molecular dissociation curves. The beauty of the theory behind this DFT basis-set correction is that it can be applied to any wave function method. The authors use their very smart idea (published in previous works) of a suitable mapping of the interaction projected in the finite basis to a long-range only interaction (erf(mu*r)/r), determining the value of the local range separated parameter mu by matching the interaction at r=0.
Here the authors further extend the DFT part of their theory by using explictilyt the on-top (OT) pair density dependence of the short-range functionals of multideterminant range separated DFT to correct the basis set error. They also show that the OT dependence can fully eliminate the spin-polarization dependence.
The idea is very neat and well explained, and the results are excellent. I recommend publication with the minor revisions below.
1) The authors should comment more the results of Table 1 for atomization energies. Although their theory is guaranteed to converge to the exact result for the complete basis set limit, the results of table 1 show that for atomization energies this does not always occur in a monotinic way. There are cases (H$_{10}$ and N$_2$ with the OT functionals, O$_2$ with all the functionals and F$_2$ with augmented basis with all the functionals) in which the results are worse for a quadruple-zeta basis than for triple zeta. Could this be due to the fact that when augmenting the basis the OT pair density from the CASSCF wavefunction does not necessarily improve but might oscillate around the Coulomb cusp creating artefacts in the extrapolated OT? After all the basis sets are optimized on the energy and do not really care about the cusp. Or is the effect due to a different accuracy of the correction for the molecule and the atoms? It would be nice if the authors could say something on that.
2) Appendix A 1: eqs. A3, as discussed by the authors may break down for the case of degenearcy of the isolated fragments. The authors comment that the spin degeneracy can be avoided by considering the functionals without spin polarization and that the spatial degeneracy can be also cured by considering for the fragment the same element of the ensemble as for the suprasystem.
However I still wonder if this is ok. For the spin I agree with the authors, but for the spatial degeneracy I still have some doubts. Could the authors comment at least qualitatively on what would happen for C$_2$ and B$_2$ for example? Is the DFT-based basis set correction going to give the same result for the spherically-averaged C or B atom than for the atoms with the occupied p orbital oritented alsong the bond axis? Or does the DFT-based correction show on this the same problems of standard DFT?
