[gmx-users] QMMM free energy

[Robert fiske]

I am looking to do QM/MM free energy calculations, first I am running tests 
with the free energy tutorial by David Mobley.  I have matched his results 
using a pure MM free energy run, and am now looking to move to the QM/MM 
step.

I added the methane molecule as my quantum system and tried running the 
first lambda.  At the steep minimization step however I get a bus error, 
using gdb it comes from nslist being 0 in new_i_nblist, the error occurs in 
the call from ns.c:979.

Looking at the code it seems that the quantum case is taken care of inside 
the condition of "!bFreeEnergy"  Inside the provided bQMM case only the coul 
pointer is passed to the function that fails, however vdwc is passed in the 
free energy code (which is set to NULL earlier in the code). So my question 
is:

Is QM/MM free energy calculation possible in the current version of gromacs 
(3.3.1 modified to work with CPMD is what I'm trying), or is there a 
parameter option to fix this type of issue?

Thank you for any help you can provide

Robert Fiske
Gogonea Group
Cleveland State University

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