re DFT and small basis sets

2003 July 1
 Re "Has anyone ever published a discussion of the accuracy of DFT at
 small basis sets?"
 I'm not sure just what you consider small (most workers now would likely
 say that
 6-31G* is small), but DFT calculations are known to be saturated by
 basis
 functions more quickly than are ab initio calculations. Here are three
 refs:
 1)  "Once the double split-valence level is reached, further improvement
 in basis
 set quality offers little in the way of structutal or energetic
 improvement." G.
 N. Merrill, S. Gronert, and S. R. Kass. J Phys Chem, 1997, _101_, 204.
 2)  "Our results also show that B3LYP calculations converge rapidly with
 increasing basis set size and that the cost-to-benefit- ratio is optimal
 at the
 6-31G* basis set level. 6-31G* will be the basis set of choice in B3LYP
 calculations on much larger molecules [than C4H6O2]." P. J. Stephens, F.
 J.
 Devlin, C. F. Chablowski, and M. J. Frisch, J Phys Chem, 1994, _98_,
 11623, and
 refs therein.
 3)  In defiance of tradition, the unequivocally small 3-21G(*) set has
 been used
 to optimize carbene geometries: H. M. Muchall, N. H. Werstiuk, and B.
 Chodhurry,
 Can J Chem, 1998, _76_, 221.
 (You my also find some useful info in E. Lewars, "Computational
 Chemistry",
 Kluwer, 2003; section 7.3.2.2).
 E. Lewars
 ========
 Ed Brothers wrote:
 > Folks:
 >     Has anyone ever published a discussion of the accuracy of DFT at
 > small basis sets?
 >
 > Ed.
 > Merz group.
 > Penn State.
 >