An improved generator coordinate Hartree-Fock method applied to the choiceof contracted Gaussian basis sets for first-row diatomic molecules

Accurate Gaussian basis sets (18s for Li and Be and 20s11p for the atoms fr om B to Ne) for the first-row atoms, generated with an improved generator c oordinate Hartree-Fock method, were contracted and enriched with polarizati on functions. These basis sets were tested for B-2, C-2, BeO, CN-, LiF, N-2 , CO, BF, NO+, O-2, and F-2. At the Hartree-Fock (HP), second-order Moller- Plesset (MP2), fourth-order Moller-Plesset (MP4), and density functional th eory (DFT) levels, the dipole moments, bond lengths, and harmonic vibration al frequencies were studied, and at the MP2, MP4, and DFT levels, the disso ciation energies were evaluated and compared with the corresponding experim ental values and with values obtained using other contracted Gaussian basis sets and numerical HF calculations. For all diatomic molecules studied, th e differences between our total energies, obtained with the largest contrac ted basis set [6s5p3d1f], and those calculated with the numerical HF method s were always less than 3.2 mhartree. (C) 2000 John Wiley & Sons, Inc.