Subject: Calculation of tensor averages

From: Marc Baaden <[email-masked]>
Date: Fri, 26 Mar 1999 00:04:00 +0100

Dear CCLers,

  I am working on the calculation of NMR shielding tensors by QM
methods.
I have calculated shielding tensors for two conformations of the same
molecule.

  Now I am looking for a way to calculate the average tensor for a given
nucleus assuming that the two conformers have equal probability.
The problem I encounter is that the geometries of the two conformers are
different (bond distances, angles etc.) and that they are differently
oriented in space. How can one calculate the average tensor ?

  More precisely:
- Does a "unique" reference frame exist, such that one can simply
calculate an average element by element : <Tij> = (Aij + Bij) / 2
  And how is it defined ?

- Has anybody already come across this problem ? And are there
literature references ?

  I would be very grateful for any hints, literature references or
comments.

Thank you in advance.

Marc Baaden

-- 
 Marc Baaden  -  Labo MSM (UMR 7551)  -  http://crypt.u-strasbg.fr/marc
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