Contracted basis sets for density functional calculations: Segmented versus general contraction

摘要

The differences between segmented and general contracted basis sets of double and triple zeta quality are analyzed for first and second row elements. Based on coverage of the exponent space and the performance for molecular properties, it is shown that a segmented contraction requires duplication of one primitive function compared to a general contraction for double zeta type basis sets. For triple zeta basis sets, segmentation necessitates either addition of one primitive function and expanding to a quadruple valence space, or addition of two primitive functions. For molecular properties depending on the valence orbitals, such as atomization energies, equilibrium distances, and vibrational frequencies, some of the inner functions describing the core orbitals can be removed without significantly affecting the accuracy. Several of the popular basis sets in common use correspond to such core-pruned basis sets. (C) 2005 American Institute of Physics.