Could anyone help me check whether the parameters and the procedures I used are right?

Hello all,

I built a model to analyze traction separation of quartz and nylon-6 interface. The lammps input file I used is revised from the lammps tutorial by Tschopp:

https://icme.hpc.msstate.edu/mediawiki/index.php/Uniaxial_Tension

I am not sure whether the parameters and the procedures I used are right. A description of the procedures and the lammps input scripts are as follows. Hopefully someone could give me some useful comments. My name is Liu Bo.

This investigation aims at analyzing the interfaces between quartz and nylon-6. A nylon-6 layer is stacked between two quartz layers in the model. The model is built as periodic in x-y plane. The surfaces of the quartz layer in z directions are covered by Si-OH groups. Two vacuum layers are added in the top and bottom of the model in z-direction so that periodic boundary conditions can also be used in z direction. Periodic boundary conditions are required by the isothermal-isobaric (NPT) ensemble that is used to equilibrate the model.

After the model is imported into LAMMPS, an energy minimization of the system is performed. Then the configuration is equilibrated using molecular dynamics in the isothermal-isobaric (NPT) ensemble at a pressure of 0 bar and a temperature of 300K for 30 ps. The configuration is then deformed by dragging the two quartz layers toward opposite directions along z-coordinate with a constant velocity. The other two simulation cell boundaries are controlled using the NPT equations of motion to zero pressure. That is, the motion of quartz layers is prescribed in the loading direction while the two orthogonal boundaries are controlled through the NPT equations. The lammps input file is as follows:

Input file for uniaxial tensile loading of nano-partical composites

Mark Tschopp, November 2010

--------------------------- units ----------------------------------

units real

dimension 3

atom_style full

boundary p p p

timestep 1

--------------------------- force field ----------------------------

pair_style lj/class2/coul/long 10 10

bond_style class2

angle_style class2

dihedral_style class2

improper_style class2

kspace_style pppm 1e-4

dielectric 1.0

special_bonds lj 0 0 1 coul 0 0 1 dihedral yes

----------------------- atom definitionh ---------------------------

read_data data.LayerOH

region 1 block 0 21.608 0 19.64 43.0 53.0 units box

region 2 block 0 21.608 0 19.64 -2.0 8.0 units box

group fixedtop region 1

group fixedbottom region 2

group boundary union fixedtop fixedbottom

group mobilezone subtract all boundary

----------------------- initialize velocity ------------------------

velocity all create 1 7655 rot yes dist gaussian

velocity all zero linear

----------------------------- modify -------------------------------

neighbor 0.3 bin

neigh_modify every 2 delay 10 check yes

----------------------- thermo setting -----------------------------

thermo 500

thermo_style custom step temp press pe ke etotal vol lx ly lz pxx pyy pzz pxy pxz pyz

timestep 1

------------------------- EQUILIBRATION ----------------------------

minimize 1e-16 1e-16 1000000000 10000000000000

------------- quench (Run for at least 10 picosecond) --------------

Constant NPT time integration via Nose/Hoover

reset_timestep 0

fix 1 all npt temp 300 300 1 iso 0 0 1 drag 1

run 30000

unfix 1

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