Hello to all my friends,
I want to obtain the stress-strain curves for a pure single-crystal aluminum (Al) sample.
according to my lammps script that is uploaded below, after the sample was completely relaxed most of the amount of stress output was negative,
I don’t know which part of the input code needs changes,
please guide me,
thanks.
lammps script for pure single crystal Al:
Please read the guidelines to avoid wasting your and our time. First of all, replace the screenshot with actual text, properly quoted as explained in the post.
Regarding your question, it may be useful to visualise the total energy, volume, and pressure during the initial equilibration phase. I would also recommend printing the stress-strain curve to a separate file, and keeping the regular thermodynamic output also for the deformation step.
To double on @hothello remarks:
- The script you share is rather useless without the results you got. We can only make guesses on what you consider faulty results from your description. I think the results are consistent with the physics in the pretty simple case.
- Performing one constant pressure simulation is not enough to relax the stress. After some equilibration at constant pressure, you need to monitor the average box lengths in the constant pressure ensemble and resize the system to these average values before starting simulation in the constant volume ensemble. Then you’ll have to check that your average pressure is zero.
- Is there a reason you modify the dt value? If not 100\ \mathrm {ps} might be short for NPT relaxation and production.