[gmx-users] QMMM free energy

[Lars Schaefer]

Robert:
With the original QM/MM implementation, free energy is currently not 
possible (yet). From what you report, I guess that also with the CPMD 
interface it does not work.
Lars

David Mobley wrote:
> Robert,
> 
> I haven't heard of anyone who has done this in GROMACS yet. My hunch
> is it will require some changes. Stay tuned to hear from the
> developers...
> 
> David
> 
> 
> On 5/29/07, Robert fiske <rfiske_ at hotmail.com> wrote:
> 
>> 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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