Response to “Comment on ‘Going beyond the frozen core approximation: Development of coordinate-dependent pseudopotentials and application to ${\rm Na}_2^+$ Na 2+’” [J. Chem. Phys. 139, 147101 (2013)

Abstract

Stoll, Fuentealba, and Szentpály (SFS) argue that the coordinate-dependent pseudopotential we developed for the sodium dimer cation molecule is inferior to other potentials that have been presented in the literature for this molecule. The goal of our work, however, was to present a novel method for the development of rigorous coordinate-dependent pseudopotentials. Our method is designed to reproduce all-electron Hartree-Fock calculations without the inclusion of adjustable parameters. Moreover, our method starts from the superposition of unoptimized, non-norm-conserved atomic potentials, so that when complete, the resulting norm-conserving potential can reproduce an all-electron Hartree-Fock calculation without the inclusion of adjustable parameters. We chose the sodium dimer cation system as a proof of principle for our method, and showed that our method does indeed allow a one-electron calculation to correctly reproduce the all-electron Hartree-Fock calculation from bonding to the dissociation limit. Our purpose in developing this method is to use such potentials in condensed-phase mixed quantum/classical molecular dynamics simulations, where inclusion of valence polarization effects is unimportant or can be added on after the fact. Thus we do not claim that our method provides a potential that is superior to potentials that have been specifically constructed to go beyond the static exchange approximation and/or include valence polarization effects-such potentials are beyond the scope of our work. We also note that although we made a numerical error in the application of our method to Na2(+) in our original work [A. Kahros and B. J. Schwartz, J. Chem. Phys. 138, 054110 (2013)] that led to an overestimation of the magnitude of core polarization effects for this particular molecule, out method does work as derived for this molecule and the error does not affect the significance of our method or its general applicability.