Accurate density-functional calculation of core-electron binding energies of some substituted benzenes

The core electron binding energies (CEBE's) of benzene, seven monosubstitut ed benzenes (Ph-X) and one disubstituted benzene (p-NH2-C6H4-NO2) were calc ulated using density-functional theory (DFT). The unrestricted generalized transition-state (uGTS) model was employed. The DeMon DFT program with a co mbined functional of Becke's exchange (B88) with Perdew's correlation (P86) was used. The average absolute deviation of the calculated CEBE's of the t itle compounds was 0.3 eV when the cc-pVDZ basis set was used. The "CEBE sh ift" of the ring carbon in Ph-X was calculated while taking the CEBE on the ring carbon in Ph-H as a reference. The thus-calculated CEBE shifts agree with experiment within the value of the average absolute deviation, 0.1 eV. The signs and quantitative numerical values of the CEBE shifts are very cl ose to the corresponding Hammett sigma constants.