[lammps-users] addforce

Hi LAMMPS Community,
I am trying to apply a pressure gradient in my simulation by applying external force on each water using addforce command in LAMMPS.
I am using real units and I want to know how this force is distributed on atom. Manual says “force will be applied on each atom of group”. In other words if I have given 1kcal/mol-A force in input files does every atom in each water will feel 1kcal/mol-A force or it is in some other.
I am worried because force is in Kcal/mol then H and O might be feeling different force that might not be very feasible for these rigid water molecules.

I am using real units and I want to know how this force is distributed on atom. Manual says “force will be >applied on each atom of group”. In other words if I have given 1kcal/mol-A force in input files does every >atom in each water will feel 1kcal/mol-A force or it is in some other.

yes, every atom

I am worried because force is in Kcal/mol then H and O might be feeling different force that might not be >very feasible for these rigid water molecules.

You could make a group with only the heavy O atoms in all the water, then use addforce on
that group. Then only the O atoms would have an added force.

Steve