Hello everyone,
I am trying to calculate shear-stress vs shear strain in Graphene. I made two group of atoms upper and lower, out of which for upper, I setforce 0, 0, 0 and for lower gave constant strain rate of 0.0001. But structure is deforming in a very strange way.
Please suggest me, what to do?
Actually, the correct way to carry out shear-strain experiments in molecular dynamics is to deform the cell simulation. Lammps has an example in its package.
By that example, I don't know how to calculate shear stress and shear strain. They are using velocity for moving the atoms as per my understanding.
Use fix deform (https://lammps.sandia.gov/doc/fix_deform.html) to deform the cell.
There are stress-strain tutorials on uniaxial stress (https://icme.hpc.msstate.edu/mediawiki/index.php/Uniaxial_Compression, https://icme.hpc.msstate.edu/mediawiki/index.php/Uniaxial_Tension). Modify the fix deform command to tilt the cell.
Thanks for your response sir. I am familiar with fix deform command for uni-axial tension/compression. But I don't know , which modification is required for shear deformation? I was trying to fix upper and lower end of the structure, and giving equal and opposite strain rate perpendicular to the fixed ends, but it is not working as two fix deform command on the same structure can't be used.
Please elaborate your response Mohsen Moeini . How change_box command can be used for shear deformation? If you have any example paper, then please mention here.
Thanks
change_box all triclinic
Use the above command. after that you can deform the simulation box in xy direction.
I do not think the commands are explained in the articles. Ask me if you have any problems.
Hope this helps.
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