LCAO DENSITY-FUNCTIONAL CALCULATIONS OF CORE BINDING-ENERGY SHIFTS OF LARGE MOLECULES

A survey of core photoelectron spectroscopy chemical shift calculations is presented. The chemical shifts are calculated at the Delta SCF level, employing the accurate LCAO-DF (X alpha) approach, and a good quality (DZP) basis set. The systems considered range from simple molecules to larger organic molecules (i.e. methyl methacrylate) and transition metal complexes; ionizations of C1s, O1s and Cr2p states are investigated. Comparison of the present results with experimental data confirms the good accuracy of the method employed. Moreover a comparison with respect to the usual quantum chemistry approach to photoionization chemical shifts (HF-Delta SCF) indicates that comparable accuracy is afforded by the LCAO-DF method which is computationally much less demanding, allowing calculations on larger systems.