Twostep method for precise calculation of core properties in molecules
Abstract
Precise calculations of core properties in heavyatom systems that are described by the operators heavily concentrated in atomic cores, such as hyperfine structure and P,Tparity nonconservation effects, require accounting for relativistic effects. Unfortunately, fourcomponent calculation of molecules containing heavy elements is very consuming already at the stages of calculation and transformation of twoelectron integrals with a basis set of fourcomponent spinors. In turn, the relativistic effective core potential (RECP) calculations of valence (spectroscopic, chemical, etc.) properties of molecules are very popular, because the RECP method allows one to treat quite satisfactorily the correlation and relativistic effects for the valence electrons of a molecule and to reduce significantly the computational efforts. The valence molecular spinors are usually smoothed in atomic cores, and, as a result, direct calculation of electronic densities near heavy nuclei is impossible. In this paper, the methods of nonvariational and variational onecenter restoration of correct shapes of fourcomponent spinors in atomic cores after a twocomponent RECP calculation of a molecule are discussed. Their efficiency is illustrated in correlation calculations of hyperfine structure and parity nonconservation effects in heavyatom molecules YbF, BaF, TlF, and PbO.
 Publication:

International Journal of Quantum Chemistry
 Pub Date:
 2005
 DOI:
 10.1002/qua.20418
 arXiv:
 arXiv:physics/0409071
 Bibcode:
 2005IJQC..104..223T
 Keywords:

 ab initio molecular calculation;
 atom in a molecule;
 electronic structure;
 molecules with heavy atoms;
 onecenter restoration;
 relativistic effective core potential;
 Physics  Atomic Physics;
 Physics  Chemical Physics
 EPrint:
 20 pages, 3 tables, lecture on the Fock schoolconference (NovgorodtheGreat, Russia, April 2004)