Hi there Community,

I'm trying to calculate the diffusion of N2 molecules in a PCN and for this purpose I must use a 3 site N2 model that is attached. The main problem I encountered is that the center of mass particle that I use has zero mass and "the dynamics can't integrate the equation of motion for a particle of zero (or small) mass."

So far I tried:

• Assigning 10^(-5) mass on the COM particle,
• Using a X forcefield type dummy atom,
• Using a point charge particle

Is there any other way to model this N2 molecule with the same properties without using a zero mass particle?