Localized orbitals in nonmetallic ring systems

• Published in: International journal of quantum chemistry Vol. 70; no. 1; pp. 167 - 180
• Main Authors: Reinhardt, P., Malrieu, J.-P., Povill, À., Rubio, J.
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 1998
• Subjects: localized orbitals; periodic structures; perturbation theory
• ISSN: 0020-7608; 1097-461X
• DOI: 10.1002/(SICI)1097-461X(1998)70:1<167::AID-QUA14>3.0.CO;2-C

Localized molecular Hartree–Fock orbitals have been determined by means of an iterative procedure consisting of orthogonalization and configuration interaction employing single excitations. For ring systems the rotational symmetry has been included explicitly to obtain Wannier‐like orbitals suited for a posteriori correlation calculations using only the most important contributions within a limited region around one reference ring segment. Applications involving different estimates of the correlation energy include as model systems (H2)2n+1, the ionic LinHn, and a weakly bound beryllium ring as well as the strongly covalent molecule (CH2)36 forming a closed ring. In all cases, the localized and canonical MP2 results are close, and the localized Epstein–Nesbet second‐order gives a good estimate of more expensive MP4 or CEPA‐0 values. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 167–180, 1998