[lammps-users] reg: SPC/E rigid water simulation

hello lammps users,

I am trying to simulate SPC/E rigid water. To define each water molecule as a rigid body I have given following commands in the input file.

group water type 1 2
fix 3 water rigid molecule

here atom type 1 is Oxygen & atom type 2 is Hydrogen…

I got the following lines in the log file…

group water type 1 2
12060 atoms in group water

fix 3 water rigid molecule
4020 rigid bodies with 12060 atoms

I understood that it is taking 3 atoms ( 1oxygen + 2 hydrogen ) as a rigid body. but my question is whether these 3 atoms belong to same molecule( have same molecule ID) or not. The following line in the fix rigid command documentation
“For option molecule, each set of atoms in the group with a different molecule ID is treated as a rigid body”
makes ask this question.

any suggestions will be appreciated…

thanks in advance…

with best regards

   hello lammps users,


the molecule id is _set_ in the data file. have a look at the documentation
for the read_data command, Atoms Section.


If you just want rigid water, use fix shake, not fix rigid.