[lammps-users] Confusion of Group ID in Group and fix rigid command

Dear User,
Here i am somewhat confused with the Group-ID in group and fix rigid command. What is the difference in the second Group-ID and value of keyword group. When i am using the two i am getting the following type of error: “ERROR: Illegal fix rigid command”. Actually i want to fixed some of the particular atom positions.

Thanking you.
apurba

Mr. APURBA MANDAL

M.Tech(Mechanical Engineer)

Ukil Bagan(Feeder Road)

Shaymnagar,North 24 Parganas

West Bengal

The fix rigid doc page explains the group-IDs used in defining the command.
If you only want to hold atoms stationary, don't use fix rigid. Just don't
integrate them, or set the force on them to 0.0 (fix setforce).

Steve