1-4 interactions

karthik_kumar · September 3, 2013, 3:03pm

HI LAMMPS users,

I have to simulate two systems A and B,

system A includes full 1-4 interactions ( 1.0) & system B doesn’t include 1-4 interactions

pair_syle is buck/coul/long.

Can anyone advice me how to set up system?

Thanks in advance

Karteek Kumar

akohlmey · September 3, 2013, 3:20pm

HI LAMMPS users,

I have to simulate two systems A and B,

system A includes full 1-4 interactions ( 1.0) & system B doesn't include
1-4 interactions

pair_syle is buck/coul/long.

Can anyone advice me how to set up system?

you cannot. that is, not without a significant amount of programming.

1-4 exclusions are handled/assigned during neighborlist creation, you
would have to write your own code to do this and figure out a way to
determine, which interactions belong to each part, etc.

axel.

karthik_kumar · September 3, 2013, 5:54pm

Thanks Axel,

As posted here by Andrew,

http://lammps.sandia.gov/threads/msg34877.html

For A type molecules (which include 1-4) and B type (doesn’t include 1-4)

Can I do the following,

use special bonds
for B-type, add pseudo bond between 1-4 atoms, and cancel out lj interactions by applying force and energies with bond_style table.

Thanks
Karteek Kumar

akohlmey · September 3, 2013, 6:54pm

Thanks Axel,

As posted here by Andrew,

http://lammps.sandia.gov/threads/msg34877.html

For A type molecules (which include 1-4) and B type (doesn't include 1-4)

Can I do the following,

1) use special bonds

2) for B-type, add pseudo bond between 1-4 atoms, and cancel out lj
interactions by applying force and energies with bond_style table.

i don't think so. you add a new bond and with it new exclusions.

axel.

karthik_kumar · September 4, 2013, 4:01pm

The above one is not working, adding an extra bond for 1-4 with table potentials to cancel out 1-4 interactions.

Surprisingly, I can see some atoms coincide with each other which is very unlikely.

( I didnt added 1-3 bond interactions via special bonds and not added 1-3 bond)

Thanks

Karteek Kumar

akohlmey · September 4, 2013, 4:37pm

The above one is not working, adding an extra bond for 1-4 with table
potentials to cancel out 1-4 interactions.

Surprisingly, I can see some atoms coincide with each other which is very
unlikely.

( I didnt added 1-3 bond interactions via special bonds and not added 1-3
bond)

but by adding this bond, you turn what was a 1-4 interaction into a
1-2 interaction (which takes precedence) and you create additional 1-3
and 1-4 pairs.

axel.