[gmx-users] CNT Potassium doping with GROMACS

[George Abadir]

Hi,
     I want to make a simulation of CNT in an environment of potassium 
atoms to see how they will be adsorbed on the CNT surface (this is a way 
of doping carbon nanotubes). I built a .pdb file with a CNT and some 
potassium atoms with random coordinates around the nanotube. When I run 
x2top to have my topology file, I get the error:"No forcefield type for 
atom K with 0 bond". The problem is that the atoms of potassium should 
indeed be not bonded to anything at the beginning of the simulation. 
Does anybody have a way to describe such a system and avoid this error?
    Thank you very much in advance,
Regards,
George