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Basis-set expansion of the Dirac equation without variational collapse: Numerical test of the forth-back free-particle Foldy-Wouthuysen transformation

Journal Article · · Phys. Rev. A; (United States)
Expansion of the Dirac operator in a finite basis set in analogy to the current matrix eigenvalue approach in nonrelativistic molecular quantum mechanics leads to unpleasant results known as ''variational collapse.'' This is avoided if one first performs a Foldy-Wouthuysen transformation to the free-particle part of the Dirac operator, then constructs the matrix representation, and transforms back ''on matrix level.'' The matrix representation so obtained has the correct ''Schroedinger limit'' for c..-->..infinity and furnishes very accurate relativistic corrections, even for moderate basis sets. This is illustrated by numerical calculations for the one-electron atom O/sup 7 +/, the H/sub 2/ /sup +/ ion, and by relativistic Hartree-Fock calculations for He and Be.
Research Organization:
Lehrstuhl fuer Theoretische Chemie, Abteilung fuer Chemie, Ruhr-Universitat Bochum, D-4630 Bochum, Federal Republic of Germany
OSTI ID:
5375904
Journal Information:
Phys. Rev. A; (United States), Journal Name: Phys. Rev. A; (United States) Vol. 28:5; ISSN PLRAA
Country of Publication:
United States
Language:
English