Dear all,
I have a bead spring model in LAMMPS and I would like to add a force on the outer two beads, pulling them apart. However, I would like this force to be oriented along the end-to-end vector between these outer beads at all time steps. Is there an easy way to implement this?
Thanks in advance!
Easy? I cannot think of one.
How many of those bead pairs are we talking about? A single one? a few? many?
How far will the be apart at full extension compared to the cutoff for non-bonded interactions?
I have 100 beads at most. The springs have a spring constant of 100, so they can be approximated as joints of a fixed length and the rest length of the springs is 1, hence the total length will not exceed 100. I do not want non-bonded interactions, so I used pair_style zero 1.
This would not be exactly what you asked for, but if there is just one chain, you can define the two end beads as a group each and then apply either fix spring or fix smd in “couple” mode.
For anything else, I suspect you will need to implement this in C++ as a new custom fix style.