[gmx-users] Energy of part of system

[Beniamino Sciacca]

Dear gmx user,
my system is: three DNA molecules solvated in water and ions.
At the end of md I would to know the interaction energy between the 
three molecules of DNA.
How can I do?
If I use g_energy and I choose "Potential" I obtain the potential energy 
of the whole system, isn't it?
But I want the interaction energy.....

Thanks in advance
Beniamino Sciacca