Subject: Re: CCL:PM3 vs. AM1 for silanes, was: MM parameters for silicon

From: "Daniel J. Berger" <[email-masked]>
Date: Mon, 21 Apr 1997 14:01:00 -0400

Simon Hogg wrote,
> Also, can anyone recommend AM1 or PM3 as more suitable for silanes?

I can recommend PM3 over AM1 for silanes, in particular for silylenes, as
long as one is after geometry rather than energies.  Energetic results for
silylenes (re. singlet-triplet gaps) are quite poor, but geometries are
quite good.  I did some calculations comparing MNDO, AM1 and PM3, for
silylenes for which good-quality ab initio results were available, as part
of my dissertation and PM3 consistently gave good geometric results.  None
of the three NDO methods I used gave good energetic results for silylenes.

I expect that PM3 energies for fully-valent silanes should be rather better
than PM3 energies of silylenes.

Will you be in Waterloo, Ontario in late May?

Daniel J. Berger       | PH: (419) 358-3379		
Bluffton College       | FAX:(419) 358-3323
280 W. College Avenue  | [email-masked]
Bluffton OH 45817-1196 | http://cs.bluffton.edu/~berger/
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