This paper is dedicuted to Professor Sigeru Huzirlugu or1 the occasion of his 65th birthdayNATHALIE GODBOUT, DENNIS R. SALAHUB, JAN ANDZELM, and ERICH WIMMER. Can J. Chem. 70, 560 (1992). Gaussian-type orbital and auxiliary basis sets have been optimized for local spin density functional calculations. This first paper deals with the atoms boron through neon. Subsequent papers will provide a list through xenon. The basis sets have been tested for their ability to give equilibrium geometries, bond dissociation energies, hydrogenation energies, and dipole moments. These results indicate that the present optimization technique yields reliable basis sets for molecular calculations.

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Local density functional (LDF) theory has been used to calculate the geometry and vibrational frequencies of a set of transition-metal compounds in their molecular forms containing halogens, oxygens, alkyl groups, carbonyls, nitrosyls, and other substituents. The calculations were done with polarized double-zeta numerical and Gaussian basis sets, and the geometries were obtained by analytic gradient methods. The frequencies were evaluated by numerical differentiation of the analytic first derivatives. The results obtained with the numerical and the Gaussian basis sets were found to be in good agreement. The agreement with experiment for the geometries is quite good with an average mean deviation of 0.026 Á. The largest errors involve dative bonds with the LDF method predicting the bonds to be too short. Nonlocal corrections were applied to some of the methyl-carbonyl and metal-nitrosyl bond lengths, and this correction was found to lengthen the bonds to give better agreement with experiment. The frequencies are also predicted quite accurately. The LDF results are in much better agreement with experiment as compared to Hartree-Fock results.

We present the theory, computational implementation, and applications of a density functional Gaussian-type-orbital approach called DGauss. For a range of typical organic and small inorganic molecules, it is found that this approach results in equilibrium geometries, vibrational frequencies, bond dissociation energies, and reaction energies that are in many cases significantly closer to experiment than those obtained with Hartree-Fock theory. On the local spin density functional level, DGauss predicts equilibrium bond lengths within about 0.02 A or better compared with experiment, bond angles, and dihedral angles to within l-2", and vibrational frequencies within about 3%-5%. While Hat-tree-Fock optimized basis sets such as the 6-3 1 G** set can be used in DGauss calculations to give good geometries, the accurate prediction of reaction energies requires the use of density functional optimized Gaussian-type basis sets. Nonlocal corrections as proposed by Becke and Perdew for the exchange and correlation energies are found to be essential in order to predict bond dissociation energies and reaction energies within a few kcal/mol. The computational efficiency of the present method together with its accuracy, which is comparable to correlated Hartree-Fock based methods, promises a great usefulness of the DGauss approach for the study of large and complex molecular structures.

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