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Multiconfigurational SCF approach for high‐symmetry molecules and its applications to fullerene trianion
Author(s) -
Kuprievich Victor A.
Publication year - 1998
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/(sici)1097-461x(1998)68:5<293::aid-qua1>3.0.co;2-q
Subject(s) - fullerene , icosahedral symmetry , symmetry (geometry) , invariant (physics) , chemistry , atomic orbital , physics , molecular orbital , molecule , quantum mechanics , electron , computational chemistry , mathematics , crystallography , geometry
A symmetry‐adapted multiconfiguration self‐consistent field (MC SCF) approach aimed at calculations of high‐symmetry molecules is proposed. The self‐consistency procedure applicable to the molecular terms of any symmetry and multiplicity is developed. It holds the symmetry transformation properties of varied molecular orbitals, thus taking advantage of the relationships within the set of two‐electron integrals through molecular invariants. For orbital optimization, a unified coupling operator is constructed on the basis of the pseudosecular method providing for efficient convergence to energy minimum. Based on the group‐theory technique, computer codes have been developed for straightforward determination of the invariant expansions for two‐electron integrals and configuration interaction (CI) matrix elements. Calculated in this way, the expansion coefficients are presented for the three‐electron states that originate from joint t 1 u and t 1 g shells of an icosahedral fullerene C 60 , the case important for the calculations of anion C 60 3− representing the charge state of the fullerene molecule in the superconducting ionic solids K 3 C 60 or Rb 3 C 60 . The results of MC SCF calculations for lowest quasi‐π‐electronic states of C 60 3− are discussed. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 68: 293–304, 1998