Accurate density-functional calculation of core-electron binding energies with a scaled polarized triple-zeta basis set. Twelve test cases and application to three C2H4O2 isomers

A scaling procedure based on Clementi and Raimondi's rules for atomic screening was proposed for atomic orbital basis sets in the unrestricted generalized transition state (uGTS) model of density functional calculation of core-electron binding energies (CEBEs). The exchange-correlation potential is based on a combined functional of Becke's exchange (B88) and Perdew's correlation (P86). This proposal was tested on CEBEs of twelve small molecules, including F-2, N-2 and H2O, and applied to the computation of CEBEs of three isomers of C2H4O2: acetic acid (CH3COOH), methyl formate (HCOO-CH3), and glycolic aldehyde (CH2OHCHO). In all cases, the new scaled pVTZ basis performs almost as well as the much larger cc-pV5Z and the average absolute difference between the results from the scaled pVTZ and estimated complete basis set limits is O.04 eV.