Determining the Equilibrium Distance in Polymer Modelling

Science Talk
1

Dear all,

I hope you are well.

I am currently investigating fiber-matrix interactions using the Lennard-Jones potential in coarse-grained simulations via LAMMPS.

To determine the values of epsilon and sigma for the pair_coeff command, I need to find the equilibrium distance, r0.

If the script is as follow:

lattice hex 1.0
region matrix block 0 50 0 50 -0.5 0.5 units lattice

How can r0 be determined please? Should it simply be the lattice value (1.0 in this case), or is it given by r₀ = lattice value / 3^0.5?

I would appreciate any insights.

Best regards,
Acer

2

Recategorized this topic since this has nothing to do with LAMMPS.

Please note that a) it is not clear from your post what you mean by “equilibrium distance” and also, please note that this value for any dynamical system is usually dependent on temperature and pressure.

3

Dear akohlmey,

Apologies for posting in the wrong section, and thank you for recategorizing it.

In the context of the Lennard-Jones potential, r0 (the minimum energy distance) is often taken as: r0=2^1/6*Sigma.

Given the following script:

lattice hex 1.0
region matrix block 0 50 0 50 -0.5 0.5 units lattice

Should r0 correspond to the lattice spacing (1.0 in this case), or should it follow r0=lattice spacing/3^0.5?

I would appreciate any insights into whether the equilibrium separation should be dictated by the lattice spacing or by the intrinsic properties of the Lennard-Jones interaction. The system is considered as a 2D representative volume element at room temperature and atmospheric pressure.

Best regards,
Acer