ACCURATE CALCULATION OF CORE-ELECTRON BINDING-ENERGIES BY THE DENSITY-FUNCTIONAL METHOD

Using a basis set of atomic natural orbitals of valence triple-zeta plus double polarization quality, the core-electron binding energies (CEBEs) of HF, H2O, N-2 and CO were computed by the deMon density-functional program with a combined functional of Becke’s exchange (B88) with Perdew’s correlation (P86). Of four different versions of the transition-state method tested, the unrestricted generalized transition-state (uGTS) model showed most promise. Two other functionals were tested but found to be inferior to the B88/P86 combination. The molecules HCN, CO2 and H2CO were added in the comparative study of basis set convergence. The best procedure found (the uGTS model using B88/P86 functional with Dunning’s cc-pV5Z basis set) was applied to other molecules. The average deviation from experiment for 20 computed CEBEs is 0.23 eV.