Subject: NMR shielding tensor problem

From: Olivier Walker <[email-masked]>
Date: Mon, 12 Feb 2001 11:25:18 +0100

Dear collegues,

I'm running some NMR calculations on  a medium size molecule (C11H8O2) using
Gaussian 98 at the MP2 level and a 6-31G basis set. The obtained results
are in
very 
good agreement with experiment (carbon-13 NMR isotropic shift appear between 0
and 220ppm)
 but when i try to use greater basis set like 6-31G* 
or 6-31G**, I obtain very strange and crazy results like:

8  C    Isotropic = -1360.4106   Anisotropy =  2054.8028
   XX=  -392.6538   YX=  1144.4672   ZX=  -223.1761
   XY=   622.5548   YY= -2190.5743   ZY=    23.5427
   XZ=  -420.8500   YZ=   254.1392   ZZ= -1498.0037
   Eigenvalues: -2609.6892 -1481.0005     9.4579

or like:

9  C    Isotropic =***********   Anisotropy =***********
   XX=***********   YX=***********   ZX=***********
   XY=***********   YY=***********   ZY=***********
   XZ=***********   YZ=***********   ZZ=***********
   Eigenvalues:*********************************

Does anybody experience the same problem with MP2 calculations?

                        Olivier.

*************************************************************
 Olivier WALKER				      	
 Laboratoire de méthodologie RMN		       
 Université de NANCY I			      
 Faculté des sciences     			      
 boulevard des aiguillettes                                     
 B.P.239-54506 Vandoeuvre les Nancy (FRANCE)
  
*************************************************************
 Tel:33.3.83.91.20.18				        
 fax:33.3.83.91.23.67				       
 E-mail:[email-masked]                
*************************************************************