Local density approximation (LDA), several popular general gradient approximation (GGA), hybrid module based density functional theoretical methods: SVWN, BLYP, PBE, HCTH, B3LYP, PBE1PBE, B1LYP, and BHandHLYP, and some nonstandard hybrid methods are applied in geometry prediction for C-60 and C-70. HCTH with 3-21G basis set is found to be one of the best methods for fullerene structural prediction. In the predictions of relative stability of C-50 isomers, PM3 is an efficient method in the first step for sorting out the most stable isomers. HCTH with 3-21G predicts very good geometries for C-50, similar to the performance of B3LYP/6-31G(d). The gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital from the predictions of all the density functional theory methods has the following descending order: E-gap(half-and-half hybrid)\> E-gap(B3LYP)\> E-gap(HCTH)(GGA)\> E-gap(SVWN)(LDA). (c) 2006 American Institute of Physics.

}, keywords = {ADJUSTABLE-PARAMETERS, BUCKMINSTERFULLERENE, C-70, DENSITY-FUNCTIONAL THEORY, ELECTRON-DIFFRACTION, ENERGIES, GENERALIZED GRADIENT APPROXIMATION, MOLECULAR-STRUCTURE, PERFORMANCE, PHASE, SEMIEMPIRICAL METHODS}, isbn = {0021-9606}, url = {The valence shell binding energy spectra and orbital electron momentum profiles of O-2 have been measured by energy dispersive multichannel electron momentum spectroscopy at an impact energy of 1200 eV + binding energy. The effects of electron correlation on the valence binding energy spectrum are investigated using multi-reference singles and doubles configuration interaction calculations. The presently reported experimental momentum profiles of O-2 display considerably improved statistics compared with previously published EMS results. The measured momentum profiles are compared with cross sections calculated using both unrestricted and restricted open shell Hartree-Fock methods with basis sets ranging from minimal to near Hartree-Fock limit in quality. In addition, the effects of correlation and relaxation on the calculated momentum profiles are investigated using multi-reference singles and doubles configuration interaction calculations of the full ion-neutral overlap distributions. Electron correlation effects in the ground state are further examined using several density functional approaches for the momentum profiles. The present EMS measurements and MRSD-CI calculations clearly show that the binding energy peak at similar to 27.3 eV has significant contributions from both (4) Sigma(u)(-) and (2) Sigma(u)(-) processes in contrast to earlier assignments which have attributed this peak to the C-2 Sigma(u)(-) State alone. Similarly, the binding energy peak at 33 eV is shown to be due to (2) Sigma(u)(-) rather than earlier assignments of (2) Pi(u) character. (C) 1998 Elsevier Science B.V. All rights reserved.

}, keywords = {CALCULATIONS, CONFIGURATION-INTERACTION CALCULATIONS, CORRELATED MOLECULAR, CORRELATION ENERGIES, DENSITY-FUNCTIONAL THEORY, DFT calculations, GAUSSIAN-BASIS SETS, HARTREE-FOCK LIMIT, OPEN-SHELL MOLECULES, PHOTOELECTRON-SPECTROSCOPY, PHOTOIONIZATION CROSS-SECTIONS}, isbn = {0301-0104}, url = {