[gmx-developers] Accessing forcefield data

[Martin Ulmschneider]

Thanks, i worked it out. Now i would like to access the c6 and c12 
values from the Lenard Jones (vdW) interaction. Could you point me to 
the right routine? I've looked at mk_nbfp in force.c, which i think has 
the cross terms for all atomtypes, but how can i find the values for 
some atom j?

Many thanks in advance!
Best wishes,
Martin

David wrote:
> On Tue, 2004-07-06 at 23:17, Martin Ulmschneider wrote:
> 
>>Hi,
>>
>>I am adding an extra force in gromacs. This force depends on the 
>>forcefield values of r0 and angle0 (i.e. the forcefield bondlength and 
>>angle). Hence i would prefer to access r0 and angle0 in the CODE rather 
>>than writing a new forcefield file loader. Is this very difficult to access?
> 
> Not very...
> There is a Urey-Bradley term in the bonded forces which should have all
> the information you need. (src/gmxlib/bondfree.c)
> 
> 
>>Best wishes,
>>Martin
>>
>>David wrote:
>>
>>>On Tue, 2004-07-06 at 21:41, Martin Ulmschneider wrote:
>>>
>>>
>>>>Hi,
>>>>
>>>>I would like to check the forcefield data (i'm interested in the 
>>>>forcefield bond lengths r0 and angles alpha0) in gromacs. Could you 
>>>>please tell me which structure they are in and how i can access them? 
>>>>E.g. the mass of atom j can be accessed by  mass = top->atoms.atom[j].m. 
>>>>Is there a simlar way to access b0 and alpha0?
>>>>
>>>
>>>wouldn't you rather browse through the text files in share/top ?
>>>otherwise you'll have to decipher the idef structure of the topology.
>>>
>>>
>>>>Many thanks!!!
>>>>Martin
>>>>
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