Subject: M: Gradients not coming down

From: A J Turner <[email-masked]>
Date: Tue, 23 Jan 1996 21:11:46 +0000 (GMT)

Hi all

I have been trying to obtain vibrational spectra from Mopac93 for 
glucosides - using both gas phase and cosmo (water) calculation.

I have encountered the following. If I use
AM1 LET GNORM=0.0001 PRECISE ??EPS=78.4?? GRADIENTS

On some of the structures - both gas phase and cosmo - the minimiser 
fails saying that a line search has failed to find a lower energy twice 
in a row or that it failed to find a lower energy even though cos has 
just been reset.

Now the final point gradients are printed out with most bond gradients 
in the order or 0.1-5 Kcal/mol.

Can anyone advise on how o get this down to a respectably low figure?

I have tried analyt - it makes no difference.  EF gives - geometery 
effectively converged - when the gnorm is still up!!

Thanks

Alex

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