On the integration accuracy in molecular density functional theory calculations using Gaussian basis sets

The sensitivity of computed DFT (Density Functional Theory) molecular prope rties (including energetics, geometries, vibrational frequencies, and infra red intensities) to the radial and angular numerical integration grid meshe s, as well as to the partitioning scheme, is discussed for a number of mole cules using the Gaussian 98 program system. Problems with typical productio n grid sizes are particularly acute for third-row transition metal systems, but may still result in qualitatively incorrect results for a molecule as simple as CCH. Practical recommendations are made with respect to grid choi ces for the energy (+ gradient) steps, as well as for the solution of the C PKS (Coupled Perturbed Kohn-Sham) equations. (C) 2001 Elsevier Science B.V. All rights reserved.