The performance of the B3-LYP variant of density functional theory when used in conjunction with the 6-31G(d) and 6-311 + G(3df, 2p) basis sets in describing the prototypical gas-phase SN2 reactions of Cl- + CH3Cl and Cl- + CH3Br has been examined in detail. Reasonable values of the complexation energies (ΔHcomp) for the ion-molecule complexes formed in these reactions are obtained. However, the overall (ΔH#ovr) and central (ΔH#cent) barriers for these reactions calculated using the B3-LYP functional are significantly underestimated when compared with G2(+) or experimental results. This implies that the B3-LYP energies for the Cl(H3C)Cl- (D3h) and Cl(H3C)Br- (C3v) transition structures are relatively too low. The B3-LYP errors appear to be systematic, with similar errors being found for corresponding quantities for the two reactions examined.
|Number of pages||7|
|Journal||Chemical Physics Letters|
|State||Published - 4 Oct 1996|
ASJC Scopus subject areas
- Physics and Astronomy (all)
- Physical and Theoretical Chemistry