On Sat, Jan 14, 2012, Dean Cuebas wrote:
>
> At the end of the Ambertools 1.5 it states that for AM1-BCC charges for
> 585 drug molecules, MOPAC and sqm give essentially similar charges for all
> the cases and the average charge difference is 0.005. So what are the
> advantages to sqm over MOPAC for AM1-BCC, since there appears to be tight
> convergence issues with sqm?
The were a number of reasons we chose sqm over mopac, the most important one
being the continuing difficulties we faced in getting mopac to compile and run
correctly on a variety of architectures and compilers. We found it to be
quite difficult to get mopac to give the same charges (say to 0.001 electron)
on different compilers, which made it frustrating to set up automated tests.
It was only after sqm was run "in the wild" on many more compounds than
we ever initially tested that we became aware of occasional convergence
issues.
By default, sqm demands tight convergence for both SCF and geometry
optimizations, whereas MOPAC has much less stringent criteria. We may not
have the most appropriate defaults, especially for am1-bcc calcs. This is
discussed in the antechamber chapter of the AmberTools Users' Manual.
....dac
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Received on Sat Jan 14 2012 - 14:30:03 PST
