1,3 and 1,4 special list while creating bonds

Hi LAMMPS users:

While using fix_bond/create to create bonds, are the 1,3 and 1,4 special lists of each atom growing? I can see in the fix_bond_create.cpp that only the 1,2 special list grows. But do other parts of the LAMMPS source codes update 1,3 and 1,4 special lists according to the changed 1,2 special list? Thanks.

Best
Shaorui

Hi LAMMPS users:

While using fix_bond/create to create bonds, are the 1,3 and 1,4 special
lists of each atom growing? I can see in the fix_bond_create.cpp that only
the 1,2 special list grows. But do other parts of the LAMMPS source codes
update 1,3 and 1,4 special lists according to the changed 1,2 special list?

i don't think so. this is why fix bond/create requires
you to use the setting: special_bonds lj/coul 0 1 1
this way, there _cannot_ be any 1-3 or 1-4 exclusions.

axel.

From the fix bond/create doc page:

This fix requires that the pairwise weightings defined by the
"special_bonds"_special_bonds.html command be 0,1,1 for 1-2, 1-3, and
1-4 neighbors within the bond topology. This effectively means that
the pairwise interaction between atoms I and J will be turned off when
a bond between them is created. It also means that the pairwise
interaction of I with J's other bond partners will be unaffected by
the new bond.

The last sentence means that 1-3 and 1-4 interactions
are not changed in the special list, nor do they need to
be, b/c of the 0,1,1 restriction.

Steve

Thanks, Steve. Then do you think if there is a way to modify this routine to forbid 1,3 and 1,4 neighbors from bonding to each other (i.e. exclude “triangle” and “quadrilateral” configs)? Thanks.

Shaorui

yes, I think that could be added as a keyword option
and check the 1-3,1-4 list when adding the bond.

Won't get to it quickly though.

Steve