[lammps-users] Langevin Thermostat Components

Hi all,
I am trying to confine the Langevin thermostat to only the x and y
components of velocity. Before there seems to be an option (axes?) for
choosing axes for thermostatting, but I cannot find that option in the
documentation for the latest version of LAMMPS. Could anyone tell me
whether there is such an option?

Thanks!

Best,
Ting

Fix temp/partial coupled to fix langevin via fix_modify
will do it. See section 4.16 of the manual for an
overview.

Steve

Hi T GE

Acturally, this question has been answered by somebody earlier. You can search it in archive for more details.

In current release, fix a langevin thermostat on specific directions can be implemented by combining “compute temp/parital” and “fix langevin”.

For example, if you want to apply langevin constraint on group ‘A’ only along Z direction, the command combination should be:

compute temp_A A temp/partial 0 0 1
fix thmfix A langevin 300.0 300.0 10e-3 34976584
fix_modify thmfix temp temp_A

Thanks for the reply!

Actually I had tried this combination of commands without obtaining
the desired result. This made me think that the temp/partial and fix
modify commands might just change the temperature for thermostatting,
not thermastatting only the selected directions. In other words, they
might just replaced the temperature used for force correction in
Langevin thermostat with a new one, but still have the force
component(s) along the unselected direction(s) corrected by the
thermostat.

Now I believe the combination indeed can thermostat the selected
directions after reading your reply. There must be some other reason
why my simulation result was unexpected.

Best,
Ting

2009/1/5, Bin Shen <[email protected]>: