@article {406, title = {Time-dependent density functional study of the static second hyperpolarizability of BB-, NN- and BN-substituted C-60}, journal = {Chemical Physics Letters}, volume = {359}, number = {5-6}, year = {2002}, note = {ISI Document Delivery No.: 576XNTimes Cited: 14Cited Reference Count: 33}, month = {Jun}, pages = {524-529}, type = {Article}, abstract = {In this work we have investigated the effects of substituting carbon atoms with B and N on the second hyperpolarizability of C-60 using time-dependent density functional theory. We have calculated the second hyperpolarizability of the double substitute-doped fullerenes C58NN, C58BB and C58BN. For C-60 only small changes in the second hyperpolarizability were found when doping with either 2B or 2N. However, by doping C-60 with both B and N, creating an donor-acceptor system, an increase in the second hyperpolarizability with about 50\% was found. (C) 2002 Elsevier Science B.V. All rights reserved.}, keywords = {benzene, CORRECT ASYMPTOTIC-BEHAVIOR, FULLERENES, HARTREE-FOCK, MOLECULAR POLARIZABILITIES, NONLINEAR-OPTICAL-PROPERTIES, PERTURBED}, isbn = {0009-2614}, url = {://000177032600027}, author = {Jensen, L. and van Duijnen, P. T. and Snijders, J. G. and Chong, D. P.} } @article {3274, title = {DENSITY-FUNCTIONAL CALCULATION OF CORE-ELECTRON BINDING-ENERGIES OF C, N, O, AND F}, journal = {Journal of Chemical Physics}, volume = {103}, number = {5}, year = {1995}, note = {ISI Document Delivery No.: RL767Times Cited: 78Cited Reference Count: 39}, month = {Aug}, pages = {1842-1845}, type = {Article}, abstract = {The unrestricted generalized transition-state model using B88/P86 functional with Dunning{\textquoteright}s cc-pV5Z basis set, found to be an excellent method of calculating core-electron binding energies (CEBEs), was further applied to many more molecules, some of which contain atoms from the third period. Estimation of relativistic corrections has also been refined. The average absolute deviation of over 50 calculated CEBEs from experiment is 0.30 eV before inclusion of approximate relativistic corrections (C-rel), and 0.23 eV after adding C-rel. Those molecules with observed CEBEs served to confirm our procedure, whereas the other cases provided our prediction of CEBEs. (C) 1995 American Institute of Physics.}, keywords = {APPROXIMATION, BASIS-SETS, DIPOLE-MOMENTS, EXCHANGE, GASEOUS ATOMS, HARTREE-FOCK, HYPERPOLARIZABILITIES, LOCAL-DENSITY, MOLECULES, POLARIZABILITIES}, isbn = {0021-9606}, url = {://A1995RL76700013}, author = {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 = {://A1991GP38800053}, author = {Casida, M. E. and Chong, D. P.} }