Premium
Variational incorporation of negative‐energy orbitals in relativistic electronic structure calculations
Author(s) -
Bunge Carlos F.,
LeyKoo Eugenio,
Jáuregui Rocio
Publication year - 2000
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 - 10.1002/1097-461x(2000)80:3<461::aid-qua16>3.0.co;2-h
Subject(s) - linear combination of atomic orbitals , slater type orbital , molecular orbital theory , atomic orbital , molecular orbital , complete active space , quantum mechanics , cubic harmonic , physics , sto ng basis sets , valence bond theory , chemistry , atomic physics , electron , molecule
Significant effects of negative‐energy orbitals in molecules with light atoms have recently been observed in calculations by perturbation theory from wave functions expressed in terms of positive‐energy orbitals. We give a detailed discussion of how to incorporate, through a rigorous variational theorem, negative‐energy orbitals in relativistic calculations of bound electronic states without any a priori knowledge of positive‐energy orbitals, neither ad hoc potentials nor self‐consistent‐field (SCF) equations. The energy contribution of negative‐energy orbitals, generally shown to be of positive sign, can be minimized by resorting to a minimax theorem or in other more practical ways, thus allowing large‐scale configuration interaction (CI) with (+) orbitals obtained from correlated calculations, rather than from uncorrelated ones as in the conventional no‐pair approach. General SCF equations are derived yielding positive‐energy orbitals in the limit of the independent‐particle model. The method is illustrated with relativistic CI calculations taken from the recent literature. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 461–470, 2000