Using FENE and quartic bonds together

LAMMPS LAMMPS Beginners
1

Hello,

I would like to ask about using FENE and quartic bonds together.

I want to use both bond types together using,

bond_style        hybrid fene quartic
bond_coeff        1 fene 30.0 1.5 1.0 1.0
bond_coeff        2 quartic 1200.0 -0.55 0.95 1.3 34.6878

but it seems like it is not allowed to use FENE and quartic together; it cannot hybridize bond styles with different topology settings.

I remember I was able to use these two bonds together using hybrid bond style before, so I just wanted to ask if there was an update regarding this.

I guess possible solution to this is to approximate FENE with quartic bond according to the parameters written in the manual,

bond_style        quartic
bond_coeff        1 1200.0 -0.55 0.25 1.3 34.6878
bond_coeff        2 1200.0 -0.55 0.95 1.3 34.6878

by using B2 as 0.25 instead of 0.95 (bond id 1 is replacing FENE here).

Please let me know if this would be fine to approach this problem.

Thank you!

2

You cannot mix bond styles that are “breakable” (like quartic) with bond styles that are not.

or use the bond_write command to create a table for the quartic bond style and use
bond style table instead.

Whatever choice you make, you need to construct some tests to validate it.

3

You may also be able to use bond_style lepton to specify an analytical expression for the bond potential, if the speed penalty is acceptable for your use case.

4

Thank you very much for the suggestions!

I will try to incorporate bond_write or bond_style lepton.

I will also try to update if I find a suitable solution to my test case.