Subject: Re: CCL:QCISD energy lower than QCISD(T) energy!

From: "Nathaniel (noj) Malcolm" <[email-masked]>
Date: Mon, 27 Apr 1998 10:22:40 +0100

you might also want to have a look at Chem. Phys. Lett. 224 (1994)195,
this paper by m. bohme and g. frenking shows another failure of
QCISD(T), this time for the dissociation of the Cu-C bond in
CuCH3. 

Again the QCISD(T) energy is found to be ABOVE that of the QCISD (for
CuCH3). This is true for both an ECP and all electron basis. Using the
same basis sets with CCSD and CCSD(T) give much more sensible
results. The authors conclude that the failure here is due to a
'wrong' estimate of the triples.

I'd highly reccomend having another look at your problems using
CCSD(T) rather than the QCISD(T)

noj

-- 
Dr. Noj Malcolm			
Theory Group,			
Dept. of Chemistry,		
University of Manchester,	
Oxford Road,			
Manchester.			
M13 9PL

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