@article {2787,
	title = {STUDY OF TRANSITION-STATE METHODS IN THE CALCULATION OF VERTICAL IONIZATION-POTENTIALS BY LOCAL-DENSITY APPROXIMATION},
	journal = {Organic Mass Spectrometry},
	volume = {28},
	number = {4},
	year = {1993},
	note = {ISI Document Delivery No.: LB163Times Cited: 37Cited Reference Count: 56},
	month = {Apr},
	pages = {321-326},
	type = {Article},
	abstract = {The vertical ionization potentials of nine small molecules were computed by the deMon density functional program and different versions of the transition-state method and the results were compared with earlier calculations and with experiment. The average absolute deviation of the 38 computed ionization potentials of the valence electrons of nine small molecules from experiment is 0.4 eV, which compares well with previous ab initio post-Hartree-Fock and semi-empirical HAM/3 calculations. The efficient methods were then used to calculate 68 ionization potentials of sixteen 22-electron molecules, with results of similar quality.},
	keywords = {KOOPMANS THEOREM, MOLECULES, PERTURBATION CORRECTIONS, PHOTOELECTRON-SPECTRA, SPECTROSCOPY, X-RAY},
	isbn = {0030-493X},
	url = {<Go to ISI>://A1993LB16300008},
	author = {Duffy, P. and Chong, D. P.}
}
@article {6980,
	title = {QUASI-PARTICLE EQUATION FROM THE CONFIGURATION-INTERACTION (CI) WAVE-FUNCTION METHOD},
	journal = {International Journal of Quantum Chemistry},
	volume = {40},
	number = {2},
	year = {1991},
	note = {ISI Document Delivery No.: FX545Times Cited: 7Cited Reference Count: 42},
	month = {Aug},
	pages = {225-242},
	type = {Article},
	abstract = {The Green-function method is a well-known way to reduce the quantum mechanical problem of n electrons moving in the field of clamped nuclei to the problem of solving a one-electron Schrodinger equation (the quasi-particle equation) involving a pseudopotential (the self-energy). This method is widely used in solid-state, low-energy electron-molecule scattering, ionization, and electron attachment theory, and much work has focused on finding accurate self-energy approximations. Unfortunately, the operator nature of the fundamental quantity (Green function) in the usual quasi-particle equation formalism significantly complicates the derivation of self-energy approximations, in turn significantly complicating applications to inelastic scattering and multiconfigurational bound-state problems. For these problems or wherever the operator approach becomes inconvenient, we propose an alternative quasi-particle equation derived wholely within a configuration interaction wave-function formalism and intended to describe the same phenomenology as does the Green function quasi-particle equation. Our derivation refers specifically to electron removal but is readily generalized to electron attachment and scattering. Although the Green function and wave-function quasi-particle equations are different, we emphasize the parallels by rederiving both equations within the equations-of-motion formalism and then producing a wave-function analog of the Green function two-particle-hole Tamm-Dancoff approximation.},
	keywords = {APPROXIMATION, CLOSED-SHELL ATOMS, CORRELATED WAVEFUNCTIONS, ELECTRON PROPAGATOR THEORY, ENERGIES, EXTENSION, IONIZATION-POTENTIALS, KOOPMANS THEOREM, MOLECULES, SCATTERING},
	isbn = {0020-7608},
	url = {<Go to ISI>://A1991FX54500005},
	author = {Casida, M. E. and Chong, D. P.}
}
@article {6979,
	title = {SIMPLIFIED GREEN-FUNCTION APPROXIMATIONS - FURTHER ASSESSMENT OF A POLARIZATION MODEL FOR 2ND-ORDER CALCULATION OF OUTER-VALENCE IONIZATION-POTENTIALS IN MOLECULES},
	journal = {Physical Review A},
	volume = {44},
	number = {9},
	year = {1991},
	note = {ISI Document Delivery No.: GP388Times Cited: 5Cited Reference Count: 81},
	month = {Nov},
	pages = {5773-5783},
	type = {Article},
	abstract = {Ab initio methods for calculating the binding-energy spectra of large molecules have traditionally been restricted to primarily either Koopmans{\textquoteright}s theorem or the density-functional transition-orbital method. The limitations of the former are well known, and the density-functonal "band-gap problem" has led to a further realization of intrinsic difficulties with the latter. An increasingly popular alternative to these two methods is to seek a simple approximation for the Green-function self-energy. The Green-function self-energy is the optical potential seen by a scattering particle (hole). As such, the dominant many-body effects contributing to the self-energy result from polarization of the charge density at energies below the first excitation energy of the target molecule (quasiparticle regime), as well as excitations of the target at higher energies. The physical importance of polarization effects is apparent in Hedin{\textquoteright}s GW approximation, which treats the self-energy as a product of the Green function (G) and a screened interaction (W) that can be calculated (essentially) from the time-dependent linear response of the charge density. In the present paper, we examine the contribution of polarization to the usual second-order Green-function (GF2) approximation with respect to the calculation of outer-valence ionization potentials in small molecules. A simplified version (GW2) of the GW approximation is found to be an acceptable substitute for the GF2 approximation, provided a self-interaction correction is included to prevent an electron from polarizing itself. Polarization effects are further analyzed using the Coulomb-hole and screened-exchange (COHSEX) and modified-COHESEX (M-COHSEX) approximations. A second-order version (M-COHSEX2) of the M-COHSEX approximation is used to examine the origin of the incorrect ordering by Koopmans{\textquoteright}s theorem of the first three ionization potentials of the nitrogen molecule in terms of static polarization and retardation effects. Finite-basis-set errors are also explored. Although higher-order Green-function approximations must be examined before drawing final conclusions, we believe that the present work provides preliminary evidence that suitably modified versions of time-dependent density-functional, dielectric-function-based self-energy approximation can be useful for molecules.},
	keywords = {BAND-GAPS, COULOMB-HOLE, EXCHANGE-CORRELATION POTENTIALS, HARTREE-FOCK, KOOPMANS THEOREM, MANY-BODY THEORY, PI-ELECTRON, pseudospectral method, SCREENED-EXCHANGE, SELF-ENERGY OPERATORS, SYSTEMS},
	isbn = {1050-2947},
	url = {<Go to ISI>://A1991GP38800053},
	author = {Casida, M. E. and Chong, D. P.}
}
