Method of recurrent construction of Löwdin spin‐adapted wave functions. III. Löwdin basis and its permutation symmetry: Evaluation of overlap integrals

Abstract

AbstractThe Löwdin basis functions are introduced and their permutation symmetry is studied in detail. A simple relation between the Löwdin basis and the orthogonal basis constructed by means of Young–Yamanouchi units is established. Both analytical and recurrence formulas for the overlap integrals of the Löwdin and some relevant auxiliary functions are derived. The symmetry of the overlap matrix of the Löwdin basis functions is briefly discussed.