[gmx-users] Make a rigid Nanoparticle

[Samieegohar, Mohammadreza]

Hi
I am trying to make a completely rigid Au nanoparticle with harmonic potential bond and angle
I am using a very big harmonic constant and still there is a small vibration in nanoparticle atoms
Do you have an idea about how can I fixe the atom totally as rigid body?
I do not want to use freeze them because my nanoparticle should move as a rigid body .

Also I have another question :
How can I make van der waals interaction zero between the nanoparticle atoms in coarse grained martini?

Thank you