Large-core vs. small-core pseudopotentials: A case study for Au2

Large-core pseudopotentials as well as model potentials may fail to properly describe bonding properties of molecules for two main reasons: (a) cores cannot be considered as frozen, and (b) core overlap cannot be neglected. This is illustrated for the case of the Au2 molecule, and it is shown how the errors can be substantially reduced by efficiently combining information from large-core and small-core calculations.