HOW to exclude coulomb interactions between specific bonded atom pairs

Hi, Lammps users,

I am using a core shell model for my system with 2 types of atoms, type 1 separate into a core part and shell part, type 2 are treated as rigid. i want to obtain the average bond length between type 1 (core), and type 2 (bond 2), so i intend to use “compute bond/local” command. However, the dilemma is the following:

The core shell model requires that the coulomb interactions between core part and shell part of type 1 (bond 1), which are bonded together, to be excluded, but i need the coulomb interactions between type 1 (core) and type 2 (bond 2). so i cannot use special bond command to exclude the coulomb interactions between bonded atom pairs simply. I am looking for a solution that lets me define both the two types of bonds above, but only excludes the coulomb interaction of bond 1, so that i can use “compute bond/local” command for bond 2. Or, if someone has better idea to compute the average bondlength of bond 2, please help me. Thanks Advance!!!

Best Regards

Jiasen Guo

I don’t understand why you need the Coulomb interaction on or off between
pairs of core/shell atoms in order to compute the current bond length.

I assume you are using the CORESHELL model in LAMMPS which
is explained at a high level in Section howto 26 (see also 25).

For that, you define bonds, and use the special_bond command.
You need the Coulomb pair off between the core/shell atoms
b/c the spring provides that interaction.

However, compute bond/local should be able to compute bond
lengths for the core/shell bonds in the usual manner.