I use lammps to build the Kremer-Great model for polymer melt, and use DPD thermostat instead of langevin equation
for some reasons, I change this model. I want to freeze some monomer, and run this model. So, I add command like this, and other commands is same:
- fix ID group-ID move linear 0.0 0.0 0.0 units box
- compute group-ID(which is free) temp
But the tempreture is lower than 1.0, and is about 0.92??
So, can lammps do this model?
If you are using pair dpd/tstat for thermostatting, it
operates on pairs of atoms and uses their relative
velocities. So I suggest you make (at least) 2 atom types.
One for frozen atoms and one for mobile atoms. You can
apply the Kremer/Grest model to both types and freeze
the one type. But I would only apply pair dpd/tstat to
the mobile type, so it is always working on pairs of mobile
atoms. The pair hybrid/overlay command can do this,
which is what you would normally use with dpd/tstat anyway.
Also, if you are computing temperature of mobile atoms
but some of them are bonded to frozen atoms, that might
affect their temperature. I.e. reduce it, since some of
the mobile atoms are not as “free” to move as they
would otherwise be.