Finding stress and load in tensile and indentation simulation

LAMMPS LAMMPS Beginners
1

Dear Experts,

I am doing tensile deformation (along z direction) simulation and want to find the longitudinal stress on the material. Is it right to use the 3rd column of the stress/atom compute and divide by the volume of the box? What will be the unit of stress in that case? According to the manual, if I am using units metal then the unit is in ‘bar’. Am I correct?

Also, how to find the indentation load for simulating nano-indentation (along z direction)? In this case, will the stress calculated in the above way and then multiplied by the xy-surface area give me load? If so, is it in units ‘bar*angstrom^2’?

Please let me know your feedback.

Thank you.

2

No. You can access the Pzz component directly in thermodynamic output.
compute stress/atom is the subdivision of the total stress to contributions from the interaction of individual atoms with its neighbors. This way you can compute contributions of subsets by summing over all atoms within a region and then dividing by the volume of that region. There is a plethora of discussions on this subject in previous posts, so you can learn from those.

3

Thanks for answer.
Are the stress or pressure given in the same units ‘bars’?

And another question: Is the definition in units command written in the restart file for further use?

4

Both questions should be answered in the documentation.