Subject: CCL:combination of b3lyp and cc-pVQZ

From: "Jens Spanget-Larsen" <[email-masked]>
Date: Thu, 30 Aug 2001 12:02:00 +0100

Frank Jensen: 

>  We have recently done some benchmarking of 
> various basis set for DFT. For the H,C,N,O,F molecules
> in the G3 data set, the MAD and Maximum error of some
> popular basis sets for total atomization energies 
> with the BLYP functional are (kJ/mol):
> 
>               MAD	Max
> 
>  6-31G*	16	64
>  cc-pVDZ	41	82
>  cc-pVTZ	3.6	14.5
>  cc-pVQZ	2.9	10.9
> 
>  These numbers are errors relative to a saturated basis
> set, i.e. the Kohn-Sham limit. 

These data are interesting. Why does cc-pVDZ perform so much worse 
than cc-pVTZ? Is this an indication that the valence-triple-zeta 
extension is physically very significant, or does the cc-pVDZ basis 
set suffer from som particular 'unbalance'? Comparison with the 
relatively satisfactory 6-31G* results might suggest that something 
is 'wrong' with cc-pVDZ.

Any similar benchmarks for Raman intensities?

Jens >--<

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JENS SPANGET-LARSEN         Office:     +45 4674 2710
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