More on Optimal Locations of Boron Atoms in the Exohedral and Endohedral C60 Fullerene

Our recent work on multiple locations of boron atoms in the exohedral and endohedral C 60 fullerene, [1], carried out within the Hartree-Fock method with the second order Møller-Plesset perturbation theory MP2 (HF-MP2), prompted recently a comment from Xu and Hou, [2], who have performed several density functional theory (DFT) calculations using DFT functionals of different complexity. In three out of five cases considered in our work, DFT calculations give the same ground state confirmations whereas in two cases optimal configurations have turned out to be different. However, depending on the choice of the exchange-correlation functional, the geometry optimization within DFT can also result in different ground state confirmations. The energy balance between nearest confirmations in these molecular complexes is subtle, and various methods can give different ground state structures. We therefore argue that the presented DFT calculations are not benchmark, and their results should be compared with ours (HF-MP2) on equal ground. We also present additional HF geometry optimizations with the 6-31G* basis set, which confirm the ground state confirmations obtained at the HF/6-31G level.