[CHM 331] NMR Calculations

[Andrew J. Pounds]

Several of you have expressed that you have had some issues with the NMR 
calculations.  Here is how you should do these.

1. Start with TMS -- optimize the molecule as directed (this may take a 
minute of two)
2. Open the output of the TMS optimization (close any other MolGroup 
windows)
3. Do the NMR calculation as requested using this optimized geometry.

Once the NMR calculation is finished, open the LOG file (not the 
checkpoint file).  If you follow the directions the file will be called 
tmsnmr.log.

Clcik on Results -> View File.   This will bring up the log file in a 
separate window.  Scroll down about halway in the file and start looking 
for the NMR data.  You are looking for the ISOTROPIC values of the GIAO 
Magnetic Shielding Tensor.  This value will be in PPM (which is what you 
read on the NMR).

There will be a value listed for each atom in your molecule.  Average 
these appropriately as described in the procedures.


For each molecule you study the process is the same. Do the 
optimization, follow that with an NMR calculation on the OPTIMIZED 
molecule, and then retrieve the values.

Once you record the values for the three molecules other than TMS, you 
can fill in the final chart where you subtract the tensor values of each 
atom from their value in TMS (this effectively puts everything on the 
same "scale").  These "subtracted" values can then be easily compared to 
the literature.




-- 
Andrew J. Pounds, Ph.D.  (pounds at theochem.mercer.edu)
Associate Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627