[lammps-users] Is there a way to put two chains together?

Dear LAMMPSers,

I now have the MD model for two independent chain set up. What I am planning to do is to artificially move one chain close to the other chain with a desired distance. After that is set, I will extract out the repulsive force one chain acted on the other one.

The way I was trying to do it is to create an artificial bond between the ends of the two chains. Is there a way to make the bond rigid other than setting the bonding coeff extremely large? Or do people know a “fix” that can better realize this scheme?

Best,
-Fei

Dear LAMMPSers,

I now have the MD model for two independent chain set up. What I am planning
to do is to artificially move one chain close to the other chain with a
desired distance. After that is set, I will extract out the repulsive force
one chain acted on the other one.

fix smd can be used to pull the two chains together.

The way I was trying to do it is to create an artificial bond between the
ends of the two chains. Is there a way to make the bond rigid other than
setting the bonding coeff extremely large? Or do people know a "fix" that
can better realize this scheme?

fix spring can be used to hold the two chains at a fixed distance.

both fix spring and fix smd operate on groups, so they can operate
on a single atom as well as on the whole chains. fix smd is in fact
derived from fix spring. both also have the facilities to extract the
applied force for averaging and computing PMFs and alike.

cheers,
   axel.