Subject: charge transfer in endohedral fullerenes

From: [email-masked] (Joachim Schulte)
Date: Tue, 7 Nov 1995 17:16:18 +0100 (CET)

Dear Ladies and Gentlemen, 

I am trying to calculate the electric field gradient of Sc in 
Sc@C82 with Gaussian 92.
Until now I have used two relatively simple basis sets:

1) STO-3G (all electron calculation) 

2) 3-21G for carbon and the Hay-Wadt ECP basis sets and ECP-potential
   for Sc. The ECP replaces 10 electrons. The basis set has been taken from 
   P. J. Hay and W. R. Wadt, J. Chem. Phys. 82, 299 (1985).

Both calculations have one common feature; they predict a quite low 
charge transfer from Sc to C82 
(about 0.8 in the case of STO-3G and 1.6 with the second
basis set). As a result an EFG is obtained which exeeds the measured one
by a factor of about 20 in the STO-3G case and by a factor of roughly 10 with
the Hay-Wadt basis set. The C82 cage geometry is C2 and the Sc-position 
is off-center by about 2 Angstroms. Also for other Sc positions the predicted 
charge transfer seems to be too low. 

Are there special basis sets which  are suitable for ionic systems?

Any helpful information on this topic would be highly appreciated. 

Sincerely Yours, 

Joachim Schulte