| Popis: |
Non-relativistic quantum mechanical ab initio calculations for polyatomic molecules have been performed for decades using the well-known basis set expansion method1 with cartesian Gaussian type Orbitals (CGTO) as the basis set. However, such calculations are meaningful, only for molecules containing light and medium atoms, since for systems involving heavy atoms (Z ≥ 70), the effects of relativity are so large (even for valence electrons) that a treatment based upon the Dirac’s relativistic equation for an electron is mandatory. The relativistic effects in molecular systems of heavy atoms have been a topic of great interest during the last decade.3–8 Recently it has been demonstrated9–11 that the basis set expansion method can be applied with success to perform Dirac-Fock-Coulomb (DFC) and Dirac-Fock-Breit (DFB) calculations for heavy atoms (assuming finite nucleus) using spherical Gaussian basis sets, which were introduced more than a decade ago12–13 in relativistic quantum chemistry. |
