Q: MM2/3 and hetero-PI-systems

[nmueller (+ at +) jk.uni-linz.ac.at (Norbert Mueller)]

 May I ask the CCL community for a little help in choosing the right
 program version for our projects - I must admit I am a bit confused.
 We have been doing force field calculations on heterocyclic and
 condesed carbocyclic aromatic systems including conjugated carbonyl
 and Schiff base groups for some time using a hoe-brew forcefiled at
 first and MM2+, a derivative of MM2 that includes part of the PI-
 electron calculations from MMPI. These programs have undergone several
 ports (mainly forced by changes in the available environments) and
 modifications to include some more hetero-atoms.
 Now we have reached a stage, where maintaining these programs has
 become rather involved. So we are considering to switch to a state of
 the art program, which should sport the following features.
 Pi-electron calcaulation including hetero-atoms (at least O and N)
         both as part of an aromatic system and as substituents
 Good parametrization of heats of formation,
         vibrational spectra are not required
 The program must be available in source form at a reasonable academic
 rate (QCPE).
 The two choices we have been considering are
 MM2(91) and MM3(?)
 Can those with experience give us some clues on the aptness of either
 of these (or alternatives) give us some recommendations?
 Thank you, I will summarize if there is interest in this
 ----------------------------------------------------------------
 Norbert Mueller - Institut f. Chemie, Johannes Kepler University
                   A-4040 Linz Austria
 e-mail: NMUELLER (+ at +) jk.uni-linz.ac.at (POP3 - Eudora - preferred)
         Norbert (+ at +) soft.uni-linz.ac.at (MacPost - for personal messages)
         norbertm (+ at +) convex.edvz.uni-linz.ac.at (unix - for BIG files)
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 "True science teaches, above all, to doubt, and to be ignorant."
                                Miguel do Unamuno