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Picture change and calculations of expectation values in approximate relativistic theories
Author(s) -
Kellö Vladimir,
Sadlej Andrzej J.
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)68:3<159::aid-qua3>3.0.co;2-u
Subject(s) - physics , coulomb , dirac equation , pauli exclusion principle , dirac (video compression format) , inverse , electric field , electron , field (mathematics) , transformation (genetics) , relativistic quantum chemistry , spin (aerodynamics) , quantum mechanics , quantum electrodynamics , mathematical physics , chemistry , mathematics , thermodynamics , geometry , biochemistry , pure mathematics , neutrino , gene
The effect of the so‐called picture change on expectation values of one‐electron operators in approximate two(one)‐component relativistic theories is discussed. This effect is expected to be particularly large for operators which assume large values in the vicinity of heavy nuclei. The numerical results illustrating the picture change effect on electric field gradients at nuclei have been obtained in the spin‐free Pauli and Douglas–Kroll approximations. It has been found that the picture change effect lowers the electric field gradient at I in HI by about 1 a.u. Very large picture change effect (−8 a.u.) has been calculated for HAt. It is concluded that in accurate calculations of expectation values of operators involving high inverse powers of the electron–nucleus distance the picture change, which accompanies the transformation of the Dirac (Dirac–Coulomb) equation to approximate two(one)‐component relativistic Hamiltonians, must be taken into account. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 68: 159–174, 1998