Istvan, Ross, Andreas, others:
It turns out that the default behavior for sqm has gradients that are not
accurate enough. If you set "grms_tol=0.0001, tight_p_conv=1,
scfconv=1.d-10," in the namelist input for sqm, you then get good behavior
with the TCNG minimizer, as expected, and as we see with MM gradients (which
are essentially exact.)
I can/will change antechamber to set stricter parameters to get AM1-BCC
charges...we'll see if this helps reduce the dependence on compiler.
But this also leaves open the question of what the defaults should be for
sqm as used in QM/MM molecular dynamics. I don't know how much testing was
done, but it is of concern that the default for tight_p_conv is zero, since
Istvan's analyis shows that this is dangerous, at least for minimization.
I'm not changing things right now, since that would probably involve updating
every one of 100 or so QM/MM test cases (sigh), but it is something that
I'd like to get comments on.
...thx...dac
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Received on Thu Dec 17 2009 - 09:30:03 PST
