MOLECULAR-ENERGIES AND PROPERTIES FROM DENSITY-FUNCTIONAL THEORY - EXPLORING BASIS-SET DEPENDENCE OF KOHN-SHAM EQUATION USING SEVERAL DENSITY FUNCTIONALS

The performance of four commonly used density functionals (VWN, BLYP, BP91, and Becke's original three-parameter approximation to the adiaba tic connection formula, referred to herein as the adiabatic connection method or ACM) was studied with a series of six Gaussian-type atomic basis sets [DZP, 6-31G*; DZVP, TZVP, TZ2P, and uncontracted aug-cc-pV TZ (UCC)]. The geometries and dipole moments of over 100 first-row and second-row molecules and reaction energies of over 300 chemical react ions involving such molecules were computed using each of the four den sity functionals in combination with each of the six basis sets. The r esults were compared to experimentally determined values. Based on ove rall mean absolute theory versus experiment errors, it was found that ACM is the best choice for predictions of both energies of reaction [o verall mean absolute theory versus experiment error (MATvEE) of 4.7 kc al/mol with our most complete (UCC) basis set] and molecular geometrie s (overall MATvEE of 0.92 pm for bond distances and 0.88 degrees for b ond angles with the UCC basis set). For routine calculations with mode rate basis sets (those of double-zeta type: DZP, 6-31G*, and DZVP) th e DZVP basis set was, on average, the best choice. There were, however , examples of reactions where significantly larger basis sets were req uired to achieve reasonable accuracy (errors less than or equal to 5 k cal/mol). For dipole moments, ACM, BP91, and BLYP performed comparably (overall MATvEE of 0.071, 0.067, and 0.059 debye, respectively, with the UCC basis set). Basis sets that include additional polarization fu nctions and diffuse functions were found to be important for accurate density functional theory predictions of dipole moments. (C) 1997 by J ohn Wiley & Sons, Inc.