How to create temperature anisotropy with thermostats

Hi all,

I am trying to find a way to create a temperature anisotropic system (say in 2 dimensions). All the particles in system are similar.
Is there anyway in lammps to thermostat x and y velocities separately?

Based on one earlier post I tried following. The input is working but Tx and Ty are not reaching to desired.

compute txx all temp/partial 1 0 0 #x temperature
compute tyy all temp/partial 0 1 0 #y temperature


velocity all create {Td} 5812775 temp new3d units box fix eq1a all langevin {Td} {Td} {trx} 334299
fix eq1b all langevin {Tdn} {Tdn} ${trx} 56849
fix eq all nve
thermo 100
fix 4 all enforce2d

fix_modify eq1a temp txx #fix my_thermostat now only operates on the x component
fix_modify eq1b temp tyy #fix my_thermostat now only operates on the y component

Is there a better and/or correct way to achieve temperature anisotropy?



You can define as many thermostats as you wish in LAMMPS.

Apply them to separate groups of atoms, or DOFs (as in your

example). There is no guarantee that just b/c you

thermostat the x DOF and y DOF separately, that the atoms

will acquire those temperatures Tx and Ty. B/c the forces

between particles instantly mix those DOFs.