The sum, w sp + w d , is close to 1.0 for both occupied and virtual COVP orbitals for metal cluster polarization, the occupied COVP orbitals for metal-to-adsorbate charge transfer as well as the virtual orbitals for the adsorbate-to-metal charge transfer. This sum is slightly smaller than 1.0 because of the inclusion of f-basis functions on metals and the use of projected orbitals in the COVP charge transfer analysis.