How to create temperature anisotropy with thermostats

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1

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

equilibrate

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?

Thanks,

Sanat

2

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.

Steve