angular velocities of water molecules

Dear lammps community,

I am interestin in rotational dynamics of water. For studying it I need to dump angular velocities. Accorring to documentation to dump it is possible to dump angular velocities only for atom_style sphere which is not compatible to typical water models. Is there any way to compute angular velocities of small rigid molecules?

Any suggestions are appreciated.

Yury Fomin

The omega() function in an equal-style variable can

calc the omega for a group of atoms. If you define

the group to be one water molecule, you will get its omega

To get an omega for each of a large number of water

molecules, you could define each of them as a chunk

and use a compute */chunk comand. There are such

computes for COM, velocity of COM, torque, gyration, etc.

However no one has yet written a compute omega/chunk.

Wouldn’t be hard to do. The compute torque/chunk is

a good starting point.


Added a compute omega/chunk and compute angmom/chunk

command. You can try them out for your water molecules.

Will be a patch later today.


Dear Steve,

Thank you very much for quick reply and very quick changed in the code. I'm going to try it now.

By the way, I sent you files with two novel pair styles for lammps, but I did not get any feedback. Could you please notify me if you have received them.

Kind regards,
Yury Fomin