Segmented Contractions of Gaussian Basis Sets for Relativistic Molecular Calculations

A method for segmented contractions of relativistic Gaussian basis sets is proposed, in which the large- and the small-component coefficients of the contracted basis sets are taken directly from the uncontracted relativistic basis sets and their kinetic balance is disregarded. The energy increases by this contraction scheme are found to be very small and the variational collapse does not occur. This method also reproduces very well the orbital energies and the radial expectation values of uncontracted basis sets. Examples of calculations on iodine (Z = 53), gold (Z = 79), and thorium (Z = 90) are reported in detail.