Dear LAMMPS users and developers
I’m conducting a tensile test on Al/Cu alloy reinforced with CNT
The potentials that I have used are

morse potential for the interaction between the C and Al, and between C and Cu

EAM for the interaction between the Al and Cu

and Airebo potential for C C interaction
The parameters of the morse potential I obtained them from the literature for AlC and CuC
What I’m expecting to get is an elongation in both the matrix and the CNT until breakage occurs in the matrix followed by a breakage at the CNT
I’ll explain what I have done so far to achieve this and what were the results 
I created the matrix with a hole at its center exactly as the diameter of the CNT and inserted the CNT in it
the minimization took place as the following 
conjugate gradient energy minimization algorithm

the composite was heated from 0 to 700 K then annealed to 300 K using fix tem/rescale

relax the structure at pressure of 0 bar and temperature of 300 K using fix npt
The result that I got from this is that the atoms of the matrix were causing an early deformation an both end of the CNT during minimization 
To fix this I put a gap between the matrix atoms and the CNT, so the hole inside the matrix is larger that the diameter of the CNT, same minimization as above was used
The result: atoms of the matrix during minimization filled fully or partially the gap between the matrix and the CNT 
to fix it, I added a wall at the inner wall of the matrix using the fix wall/region lj93, it was applied on the matrix atoms and the region was of the matrix as well, the minimization was as above
The result: the CNT moved and got stuck to one side of the matrix 
I added a fix move linear on the atoms of the CNT with velocities at x and y were fixed to zero so the cnt will stay at the center of the matrix, same minimization steps as above
The result: atoms were lost from the CNT 
I added the wall/region as above on the inner side of the matrix, and fix move linear on the cnt atoms and did the minimization for the matrix atoms only
using the following steps of minimization 
conjugate gradient energy minimization algorithm

relax the structure at pressure of 0 bar and temperature of 300 K using fix npt
This was followed by removing the fix move linear and minimizing the CNT atoms only
Then the deformation was applied as following
fix 1 all nvt temp 300 300 $(100.0*dt)
fix 3 all deform 1 z erate ${strate} units box remap x
The result: the CNT had perfect structure and stayed at the center after minimization but during deformation instead of having the elongation on the composite, all atoms were moving horizontally and leaving the simulation cell and entering again
 In the deformation I changed nvt to fix all langevin
The result: elongation occurred but it caused a collapse at both ends of the CNT instead of breakage at the center
Please advise
Regards
Isra