The basis set convergence of the density functional energy for H-2

The convergence of the density functional energy of Hz is shown to be expon ential with respect to basis set size from results obtained with fully opti mized basis sets. The convergence is slightly slower than for the Hartree-F ock energy, but the basis set requirements are very similar. The variation in optimal exponents between different density functional methods is simila r to that between different molecules for the Hartree-Fock method. The resu lts indicate that hierarchical basis sets for systematically approaching th e Hartree-Fock limit an likely also to be suitable for estimating the basis set limit for density functional methods. (C) 2000 Elsevier Science B.V. A ll rights reserved.