[gmx-users] who can help me with the force-field?

[Mark Abraham]

xiao shijun wrote:
> Hi everyone,
>     Recently, I met a problem on the force-field. I am doing something 
> on the calcium carbonate, and want to simulation it with gromacs.
> The shell model for oxygen has been emploied in my system. When I 
> considered the non-boned potential associated with interactions between 
> atoms
> in the same CO3 group, I only need to take O-O buckingham interaction 
> into account, but any electric interaction. How could I realize that in 
> my .top file.
>     First, I tried to use [pairs] to eliminate electric interaction, but 
> I can't add the buckingham interaction of O-O because there is no 
> buckingham
> options for LJC14. I want to know if anyone of you have such the 
> experience. Thanks!!

Usually you would not define a nonbonded interaction for atoms that are 
so close together, since their interaction should be able to be modelled 
adequately with the C-O bond and O-C-O angle (and perhaps with CHARMM, 
an interaction harmonic the O-O distance as a Urey-Bradley term).

Mark