[gmx-users] gromacs QMMM gaussian 09 (g09) input format

Stanislav Šimko stanislav.simko at gmail.com
Sun Nov 23 11:36:23 CET 2014

Dear gromacs users/authors
I'm trying to run gromacs with QMMM support (so far I tried
g09,orca,mopac) and the best I could do is run test simmulation (spc
water box, 213 molecules) only with g09 (gromacs with mopac support
fails to compile, test simulation with orca fails with seg. fault after
orca finishes calculation but it is possible that my settings for orca
are bad, i tried orca only now).
	Unfortunately, this simulation is unstable - QM atoms moves too fast
and (eventually, after some time calculation crashes because gromacs
sends to gaussian molecule with atoms that are 10nm away from each
other). For me it looks like gradients read from fort.7 are in different
units/ are something completely different than gromacs expects. 
Could you please help me where I can find what format (units, what
interactions needs to be included) gromacs expects from gaussian? It is
not obvious for me from gromacs source code. 
Or maybe if you could help me how to modify gaussian source code? (i saw
roadmap.pdf but this is for g03 and I can't find lot of those
functions/equations in g09, therefore I didn't try to change those I
could find in g09 yet. Also I tried to compile g03 with gfortran but
without any luck)

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