Generalized Relativistic Effective Core Potentials for superheavy elements.

N.S.Mosyagin, A.V.Titov, A.N.Petrov, T.A.Isaev
Petersburg Nuclear Physics Institute

Investigation of physical and chemical properties of relatively long-living
isotopes of SuperHeavy Elements (SHE) from an "island of stability" (with
nuclear charges Z=108 to 118), some of which were recently synthesized
by Oganessian's group [1], and their compounds is a fundamental scientific
problem. The SHE properties are very difficult for the experimental study
because of their extremely small quantities, only single atoms are available
for research now. Therefore, precise calculations on SHE compounds are
necessary to gain a better understanding of their physics and chemistry,
which, as is already known, are essentially different from those of their
lighter homologues by the valence structure [2,3]. The relativistic
pseudopotential or Relativistic Effective Core Potential (RECP) method is
one of the most optimal approaches for calculations on molecules
containing heavy atoms [4]. In a series of papers [5,6], we have
introduced and developed the Generalized RECP (GRECP) technique.
This method is described in detail in papers [6] and it allows one to attain
practically any desired (high) accuracy, while requiring moderate
computational efforts. It is known that the Breit interaction can contribute
a few hundreds wave numbers even to transition energies between
low-lying states of very heavy elements. Undoubtedly, this contribution
should be taken into account at precise calculations of such systems. For a
series of SHE, we constructed GRECPs [3] which effectively incorporate
the Breit effects. In order to estimate the accuracy of these GRECPs,
calculations of transition energies for these atoms were carried out.
Significant improvement of the accuracy in reproducing the all-electron
Dirac-Hartree-Fock-Breit results for the GRECP as compared to the
tested RECPs of other groups was demonstrated in these calculations.
The same number of electrons is explicitly treated in the considered RECP
versions.
A.T. and N.M. were supported in part by Scientific Program of
St.Petersburg Scientific Center of RAS. T.I. is grateful to INTAS grant
YSF 2001/2-164 for financial support. A.P. is grateful to Ministry of
education of Russian Federation (grant PD02-1.3-236) and to
St-Petersburg Committee of science (grant PD02-1.3-236). This work
was supported in part by RFBR grant 03-03-32335.

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     Adv.Quant.Chem. 31, 313 (1999).
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     Accuracy and efficiency of modern methods for electronic structure
     calculation on heavy- and superheavy-element compounds,
     Eprint http://xxx.lanl.gov/abs/physics/0209035; accepted for
     publication in russian journal "Nuclear Physics".
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