@article {2591,
	title = {An evaluation of exchange-correlation functionals for the calculations of the ionization energies for atoms and molecules},
	journal = {Journal of Electron Spectroscopy and Related Phenomena},
	volume = {171},
	number = {1-3},
	year = {2009},
	note = {ISI Document Delivery No.: 452BQTimes Cited: 6Cited Reference Count: 82Segala, Maximiliano Chong, Delano P.},
	month = {Apr},
	pages = {18-23},
	type = {Article},
	abstract = {In this paper, ionization energies of gas-phase atoms and molecules are calculated by energy-difference method and by approximate transition-state models with density functional theory (DFT). To determine the best functionals for ionization energies, we first study the H to Ar atoms. An approximation is used in which the electron density is first obtained from Kohn-Sham computations with an exchange-correlation potential V-xc known as statistical average of orbital potentials (SAOP), after which the energy is computed from that density with 59 different exchange-correlation energy functionals E-xc. For the 18 atoms, the best E-xc functional providing an average absolute deviation (AAD) of only 0.110 eV is one known as the Krieger-Chen-lafrate-Savin functional modified by Krieger, Chen, Iafrate, and Kurth, if one uses the spin-polarized spherical atom description. On the other hand, if one imposes the condition of integer-electrons, the best functional is the Becke 1997 functional modified by Wilson, Bradley, and Tozer, with an AAD of 0.107 eV, while several other functionals perform almost as well. For molecules, we can achieve an accuracy of AAD = 0.21 eV for valence VIPs of nonperhalo molecules with Delta E(V-xc = SAOP;PBEO) using integer-electron description. For perhalo molecules our best approach is Delta E(V-xc from either E-xc or SAOP;mPW1PW) with full symmetry to obtain an AAD = 0.24 eV. (c) 2009 Elsevier B.V. All rights reserved.},
	keywords = {ADJUSTABLE-PARAMETERS, ASYMPTOTIC-BEHAVIOR, DFT, Energy-difference method, EXCITATION-ENERGIES, GENERALIZED GRADIENT APPROXIMATION, HE(II) PHOTOELECTRON-SPECTRA, Integer-electron, Ionization energy, models, ORBITAL MODEL POTENTIALS, ORGANIC-MOLECULES, PHOTO-ELECTRON SPECTRA, Slater-type orbitals, Spin-polarized spherical atom, STATISTICAL AVERAGE, TRANSITION-STATE},
	isbn = {0368-2048},
	url = {<Go to ISI>://000266515000002},
	author = {Segala, M. and Chong, D. P.}
}
@article {350,
	title = {Interpretation of the Kohn-Sham orbital energies as approximate vertical ionization potentials},
	journal = {Journal of Chemical Physics},
	volume = {116},
	number = {5},
	year = {2002},
	note = {ISI Document Delivery No.: 514CGTimes Cited: 203Cited Reference Count: 81},
	month = {Feb},
	pages = {1760-1772},
	type = {Article},
	abstract = {Theoretical analysis and results of calculations are put forward to interpret the energies -epsilon(k) of the occupied Kohn-Sham (KS) orbitals as approximate but rather accurate relaxed vertical ionization potentials (VIPs) I-k. Exact relations between epsilon(k) and I-k are established with a set of linear equations for the epsilon(k), which are expressed through I-k and the matrix elements epsilon(k)(resp) of a component of the KS exchange-correlation (xc) potential v(xc), the response potential v(resp). Although -I-k will be a leading contribution to epsilon(k), other I-jnot equalk do enter through coupling terms which are determined by the overlaps between the densities of the KS orbitals as well as by overlaps between the KS and Dyson orbital densities. The orbital energies obtained with "exact" KS potentials are compared with the experimental VIPs of the molecules N-2, CO, HF, and H2O. Very good agreement between the accurate -epsilon(k) of the outer valence KS orbitals and the corresponding VIPs is established. The average difference, approaching 0.1 eV, is about an order of magnitude smaller than for HF orbital energies. The lower valence KS levels are a few eV higher than the corresponding -I-k, and the core levels some 20 eV, in agreement with the theoretically deduced upshift of the KS levels compared to -I-k by the response potential matrix elements. Calculations of 64 molecules are performed with the approximate v(xc) obtained with the statistical averaging of (model) orbitals potentials (SAOP) and the calculated epsilon(k) are compared with 406 experimental VIPs. Reasonable agreement between the SAOP -epsilon(k) and the outer valence VIPs is found with an average deviation of about 0.4 eV. (C) 2002 American Institute of Physics.},
	keywords = {ASYMPTOTIC-BEHAVIOR, DENSITY-FUNCTIONAL THEORY, DERIVATIVE DISCONTINUITIES, ELECTRON BINDING-ENERGIES, EXCHANGE-CORRELATION POTENTIALS, HE(II), LOCAL POTENTIALS, MODEL POTENTIALS, ORGANIC-MOLECULES, PHOTOELECTRON-SPECTRA, STATISTICAL AVERAGE},
	isbn = {0021-9606},
	url = {<Go to ISI>://000173418600003},
	author = {Chong, D. P. and Gritsenko, O. V. and Baerends, E. J.}
}
