A method is presented for localizing canonical HF molecular orbitals to obtain physically meaningful orthogonal 'quasi-bond orbitals' (QBO). Atomic hybrids and nonorthogonal bond orbitals (BO) are defined according to a well-established procedure. The transformation of the HF MO is such that the resulting QBO resemble as closely as possible the BO. With respect to the BO, the QBO have the advantage of being orthogonal and optimized at the HF level. Tests run with a selected CI algorithm (CIPSI) on the two anions [CH2---NH2---CH2]- and [NH2---CH2---CH2]- show how convenient it is to use QBO in CI calculations. The resulting CI wavefunctions lend themselves to a clear physical interpretation.
Quasi-bond orbitals from maximum-localizzation hybrids for ab initio calculations
ANGELI, Celestino;
1995
Abstract
A method is presented for localizing canonical HF molecular orbitals to obtain physically meaningful orthogonal 'quasi-bond orbitals' (QBO). Atomic hybrids and nonorthogonal bond orbitals (BO) are defined according to a well-established procedure. The transformation of the HF MO is such that the resulting QBO resemble as closely as possible the BO. With respect to the BO, the QBO have the advantage of being orthogonal and optimized at the HF level. Tests run with a selected CI algorithm (CIPSI) on the two anions [CH2---NH2---CH2]- and [NH2---CH2---CH2]- show how convenient it is to use QBO in CI calculations. The resulting CI wavefunctions lend themselves to a clear physical interpretation.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.