polymer model, FENE, bond+DPD

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1

I am implementing a polymer model with DPD: all atoms are interacting in
DPD style^{1} and some pairs of atoms have extra FENE^{2} force.

My problem is the following. I cannot keep both DPD and FENE interactions
for one pair. I've played with special_bonds command but without
success. Here is a minimal example.

Two atoms interacting with DPD force
nobond.initial
nobond.lammps

Two atoms with FENE bound. But I have no DPD interaction.
bond.initial
bond.lammps

[1] http://lammps.sandia.gov/doc/pair_dpd.html
[2] by FENE I mean this force http://en.wikipedia.org/wiki/FENE
   or http://lammps.sandia.gov/doc/bond_fene.html with
   epsilon = 0

nobond.initial (448 Bytes)

nobond.lammps (355 Bytes)

bond.initial (489 Bytes)

bond.lammps (399 Bytes)

2

I don't understand what you are asking. You can use
pair_style dpd and bond_style fene together.

Steve

3

Thank you for the tip. I found solution.
Adding
special_bonds lj 1 1 1
works for DPD.