Dear LAMMPS Users,
In my research project I have a graphene sheet in the middle of a box on xy plane which is infinite only along x direction and polymer inside the box with periodic boundary conditions in all directions.
In my lammps data file I have defined the bonds, angles, and dihedrals explicitly and for the infinite direction of the graphene sheet because of the potential with explicit bonds.
I am equilibrating the system in NPT with allowing only z dimension relax to reach the correct density at low temperature. (Y dimension of the box is larger than graphene width in this direction and kept fixed along with the X dimension). Lammps doesn’t give any warnings during the equilibration.
After it has reached to the correct temperature, I apply uniaxial tensile straining along y direction of the box. (Using change_box command).
However when I calculate the Stress components, the stress in the straining direction (y direction) of the graphene sheets shows a compression in the middle. This is only for some of the x lengths of the graphene sheet (In the infinite direction). And for some x lengths of the graphene sheet, this stress shows tension in the middle of the sheet which is the expected. It doesn’t look like a problem due to polymer equilibration because of the visual observations and the polymer density calculations show correct data.
At this moment, I have rechecked the code which I have been using to generate the input structures for possible errors and there is none that I could see.
Please let me know if there is anyone who encountered a similar problem or any suggestions to find out the reason behind this or anything to do with the lammps distribution I am using. (lammps-15May15)