Can I use fix shake command to fix 5 atoms?

Hello author,

I’m trying to use lammps to study material annealing, and in my study process, I want to fix some groups but not ‘fix group’ command, because I want them to do the whole movement. so I want to use ’ fix shake ‘command. In the manual, it said ’ LAMMPS allows for the following kinds of clusters to be constrained: one central atom bonded to 1 or 2 or 3 atoms, or one central atom bonded to 2 others and the angle between the 3 atoms also constrained’. But my clusters have five toms, for example phosphate ( PO4 ), so I don’t know how to 'fix shake ’ the clusters. Do you have some suggestions? And I’m very glad for you response. Thank you very much!


no, you can’t, as the fix shake doc page says. You can try fix rigid/small
to see if it does what you want.