Ab initio and density functional theory calculations of the dipole polarizabilities of ethene, benzene and naphthalene

Geometries and static dipole polarizabilities alpha and polarizability anisotropy Delta alpha of ethene, benzene and naphthalene have been investigated by ab initio and density functional theory (DFT) methods using a variety of basis sets. In DFT calculations contributions to the exchange energy were estimated by the Slater (S), Becke (B) and hybrid Becke (B3) functionals. Exchange-correlation effects were estimated by combining these functionals with the Vosko, Wilk and Nusair (VWN) and Lee, Young and Parr (LYP) correlation functionals. Excellent agreement is found between the DFT results and the available experimental and high level correlated ab initio data, particularly when the B3LYP functional is used in conjunction with the aug-cc-pVDZ basis in molecular structure calculations and with the specifically designed HUZ-SV(+sd+sp) basis in polarizability calculations, CC bond lengths being predicted with Delta r rms = 0.007 Angstrom and mean dipole polarizability within 1-2% of the experimental value. The relative performance of the functionals increases in the order: S-null < B-null < B3-null < BLYP < SVWN < B3LYP. The exchange part of the functional appears to be dominant and tends to increase [alpha] and Delta alpha values, the correlation part acting in balancing it. The molecular geometry plays a crucial role. Proper calculations carried out in ethene show that a great part of the correlation effects on [alpha] and Delta alpha are encompassed in Hartree-Fock (HF) calculations which use the correlated geometry. (C) 1998 Elsevier Science B.V.