Generalized Relativistic Effective Core Potential Method: Theory and calculations
Abstract
In calculations of heavyatom molecules with the shapeconsistent Relativistic Effective Core Potential (RECP), only valence and some outercore shells are treated explicitly, the shapes of spinors are smoothed in the atomic core regions and the small components of fourcomponent spinors are excluded from calculations. Therefore, the computational efforts can be dramatically reduced. However, in the framework of the standard nodeless radially local RECP versions, any attempt to extend the space of explicitly treated electrons more than some limit does not improve the accuracy of the calculations. The errors caused by these (nodeless) RECPs can range up to 2000 $cm^{1}$ and more for the dissociation and transition energies even for lowestlying excitations that can be unsatisfactory for many applications. Moreover, the direct calculation of such properties as electronic densities near heavy nuclei, hyperfine structure, and matrix elements of other operators singular on heavy nuclei is impossible as a result of the smoothing of the orbitals in the core regions. In the present paper, ways to overcome these disadvantages of the RECP method are discussed. The developments of the RECP method suggested by the authors are studied in many precise calculations of atoms and of the TlH, HgH molecules. The technique of nonvariational restoration of electronic structure in cores of heavy atoms in molecules is applied to calculation of the P,Todd spinrotational Hamiltonian parameters including the weak interaction terms which break the symmetry over the space inversion (P) and timereversal invariance (T) in the PbF, HgF, BaF, and YbF molecules.
 Publication:

arXiv eprints
 Pub Date:
 August 2000
 arXiv:
 arXiv:physics/0008160
 Bibcode:
 2000physics...8160T
 Keywords:

 Physics  Chemical Physics;
 Physics  Atomic Physics;
 Physics  Computational Physics
 EPrint:
 22 pages, latex, no figures