Compact effective potentials and efficient shared‐exponent basis sets for the first‐ and second‐row atoms

Compact effective potentials, which replace the atomic core electrons in molecular calculations, are presented for atoms in the first and second rows of the periodic table. The angular-dependent components of these potentials are represented by compact one- and two-term Gaussian expansions obtained directly from the appropriate eigenvalue equation. Energy-optimized Gaussian basis set expansions of the atomic pseudo-orbitals, which have a common set of exponents (shared exponents) for the s and p orbitals, are also presented. The potentials and basis sets have been used to calculate the equilibrium structures and spectroscopic properties of several molecules. The results compare extremely favorably with corresponding all-electron calculations.