LIMITATIONS OF CURRENT-DENSITY FUNCTIONAL THEORIES FOR THE DESCRIPTION OF PARTIAL PI-BOND BREAKING

It is shown on the example of the torsional potential of butadiene, th at several density functionals including gradient corrected non-local functionals exhibit an intrinsic error that leads to the overestimatio n of rotational barriers due to partial pi-bond breaking. This problem occurs for all functionals investigated including SVWN, BLYP, B3LYP, BPL and BP86 and is independent of the basis set. The hybrid exchange functional (B3) is slightly better than the others, These errors are a bsent for torsional potentials around single bonds, such as in 1-buten e and indicates that the problem may be related to the overestimation of conjugation energy. (C) 1997 Elsevier Science B.V.