Besley, Nicholas A.Gilbert, Andrew T. B.Gill, Peter M. W.2015-11-252015-11-250021-9606http://hdl.handle.net/1885/16803The accuracy of core excitation energies and core electron binding energies computed within a Δself-consistent-field framework is assessed. The variational collapse of the core excited state is prevented by maintaining a singly occupied core orbital using an overlap criterion called the maximum overlap method. When applied to a wide range of small organic molecules, the resulting core excitation energies are not systematically underestimated as observed in time-dependent density functional theory and agree well with experiment. The accuracy of this approach for core excited states is illustrated by the calculation of the pre-edge features in x-ray absorption spectra of plastocyanin, which shows that accurate results can be achieved with Δself-consistent-field calculations when used in conjunction with uncontracted basis functions.N.A.B. is grateful to the ANU for a 2007 Visiting Fellowship.http://www.sherpa.ac.uk/romeo/issn/0021-9606..."Publishers version/PDF may be used on author's personal website, institutional website or institutional repository" from SHERPA/RoMEO site (as at 26/11/15). Copyright 2009 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in The Journal of Chemical Physics and may be found at https://doi.org/10.1063/1.3092928Keywords: Binding energy; Electric excitation; Electromagnetic wave absorption; Excitation energy; Excited states; Basis functions; Core electron binding energies; Core-excitation energies; Core-excited state; Plastocyanin; Pre-edge features; Self-consistent fields2009-03-2510.1063/1.30929282016-02-24