PNO–CI (pair‐natural‐orbital configuration interaction) and CEPA–PNO (coupled electron pair approximation with pair natural orbitals) calculations of molecular systems. IV. The molecules N2, F2, C2H2, C2H4, and C2H6

摘要: SCF, IEPA–PNO, CEPA–PNO, and PNO–CI calculations have been performed for the molecules N2 F2 at their experimental equilibrium distances with two basis sets, a ’’small’’ that contains one d set per atom ’’standard’’ sets f set. Potential curves of these are calculated small sets. The C2H2 C2H4 (which additionally p on H) ’’hydrocarbon’’ is smaller in s,p part, but includes same polarization functions. For C2H6 both its staggered eclipsed forms only hydrocarbon used. computed correlation energies analyzed terms quantities defined Part I, particular, IEPA pair eμIEPA error ΔEIEPA energy. A comparison made between results canonical localized representations partially description which σ–π separation preser...