I want to relax one crystal unit to get its crystal parameters by using "fix 1 all box/relax iso 0.0 vmax 0.001" and fix the y parameter at the same time. How to alter the command to achieve that? Thanks in advance.
Dear Hancheng, thank you for posting this interesting technical question. Please have a look at the following potentially useful link which might help you in your analysis:
https://matsci.org/t/lammps-users-crystal-relaxation-centro-symmetric-parameter/5779
Good luck with your worK!
Hi Frank, thanks for your help!
I check the link and minimization method was used in the link so the unit box parameters were fixed. However, in my case I want to relax the box as well (with y fixed).
Maybe this is what you are wanting?
fix 1 all box/relax x 0.0 z 0.0 couple xz vmax 0.001
From the LAMMPS documentation page https://docs.lammps.org/fix_box_relax.html:
The target pressures Ptarget for each of the 6 components of the stress tensor can be specified independently via the x, y, z, xy, xz, yz keywords, which correspond to the 6 simulation box dimensions. For example, if the y keyword is used, the y-box length will change during the minimization. ... A box dimension will not change if that component is not specified.
The couple keyword allows two or three of the diagonal components of the pressure tensor to be “coupled” together. The value specified with the keyword determines which are coupled. For example, xz means the Pxx and Pzz components of the stress tensor are coupled.
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