method to use Fix NVT

Dear LAMMPS Users & Developers
I want to simulate interaction of tow different material at their interface by using Reax potential.
my simulation box contain 2 region and one crystal in each of region and contact in interface.
I used one “fix nvt” and thermostat for all simulation box during equilibration and also used one “fix nvt” during loading.
Now I think, because of diffrent behavior and temperature fluctuation in each material maybe it is convenient to compute temperature for each material and use fix nvt (or npt) and thermostat for each material seperatly, But I am worry there is a basically problem for this method.
I apologise to ask this question that is not direct relation to LAMMPS Code, but I want to know is it reasonable to use this method espicialy at interface?
Best regards
Hadi

I don't understand what you mean specifically. Do you want
both interfaces to have different temperature or different damping
parameters?

I guess that the first one is extremely model-dependent. I mean, do
you want them to be in thermal equilibrium? is there any effective
temperature gradient that you want to model as two different
temperatures?

If you want to have different damping parameters, I don't think
there is actually any need for both of them to have the same value.

pablo

2013/7/2 Hadi Sedaghat <[email protected]>:

Dear Pablo
Thanks for your reply and I’m sorry that I could not ask the question well.
If the final temperature, gradiant and damping parameters are same, is there any
diffrence to use one “fix nvt” command for all simulation box that contain tow
crystals (mat1 & mat2) and interact at one side or use tow “fix nvt” command for each crystal.(following commands)
Thanks
Hadi

compute tempmat1 boxmat1 temp
compute tempmat2 boxmat2 temp
velocity boxmat1 create 100 12345 temp tempmat1 mom yes rot yes dist gaussian
fix fixstep11 boxmat1 nvt temp 100 300 0.1
fix_modify fixstep11 temp tempmat1
velocity boxmat2 create 100 12345 temp tempmat2 mom yes rot yes dist gaussian
fix fixstep12 boxmat2 nvt temp 100 300 0.1
fix_modify fixstep12 temp tempmat2

or

compute tempmat boxmat temp
velocity boxmat create 100 12345 temp tempmat mom yes rot yes dist gaussian
fix fixstep1 boxmat nvt temp 100 300 0.1
fix_modify fixstep1 temp tempmat

Sure there is a difference. LAMMPS will
let you use N thermostats if you wish,
each on 1/N atoms in the simulation. N can
be 1,2,…10 if you like. It’s up to you to
decide which of those scenarios makes
sense for your model. Nose/Hoover (NVT)
is a “global” thermostat in the sense
the new velocities of all the atoms in the
group depend on all the velocities of
atoms in that group. So if the group
is different, the behavior of the thermostat
is (maybe slightly, maybe greatly) different.

Steve