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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 Super-Heavy Elements (SHE) from the "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 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.

[1] Yu.Ts.Oganessian, et al., Nature 400, 242 (1999);  Nature 413, 122 (2001);     K.Powell, Nature 418, 815 (2002); Ch.E.Dullmann, et al., Nature 418, 859 (2002).
[2] U.Kaldor and E.Eliav, Adv.Quant.Chem. 31, 313 (1999).
[3] A.V.Titov, N.S.Mosyagin, T.A.Isaev, A.N.Petrov, Phys.At.Nucl.
     66, 1152 (2003).
[4] W.C.Ermler, R.B.Ross, P.A.Christiansen, Adv.Quant.Chem. 19, 139 (1988).
[5] I.I.Tupitsyn, N.S.Mosyagin, A.V.Titov, J.Chem.Phys. 103, 6548 (1995);     N.S.Mosyagin, A.V.Titov, Z.Latajka, Int.J.Quant.Chem. 63, 1107 (1997).
[6] A.V.Titov and N.S.Mosyagin, Int.J.Quant.Chem. 71, 359 (1999); A.V.Titov and N.S.Mosyagin, Rus.J.Phys.Chem. [Zh.Fiz.Khimii] 74 (Suppl. 2), S376 (2000).