doubt in compute chunk

hello users,

I have a mixture consisting two liquids(liq1+liq2)confined between graphite sheets ,initially i run the system at 600k to relax the system and then compute the density using the following commands:once i get the density profile symmetric in this temperature i tried to anneal the system slowly,but still the density profiles are not coming symmetric.is there any thing wrong in the command.I want the system temperature to be 400 K . why the annealing the is not done properly? any suggestions!help!!!

velocity liqui create 600.0 4928459 rot yes mom yes dist gaussian
velocity mysheet create 600.0 4928459 rot no mom no dist gaussian
velocity mysheet zero linear
fix 1 ionic nvt temp 600 600 100.0 drag 0.2

compute cc3 liq1 chunk/atom bin/1d z -3.35 0.5 units box
fix zden3 liq1 ave/chunk 10 10000 100000 cc3 density/mass file liq1.profile ave running

compute cc4 liq2 chunk/atom bin/1d z -3.35 0.5 units box
fix zden4 liq2 ave/chunk 10 10000 100000 cc4 density/mass file liq2.profile ave running

run 5000000
unfix 1

fix 2 ionic nvt temp 600 580 100.0 drag 0.2

compute cc5 liq1 chunk/atom bin/1d z -3.35 0.5 units box
fix zden5 liq1 ave/chunk 10 10000 100000 cc5 density/mass file liq1.profile ave running

compute cc7 liq2 chunk/atom bin/1d z -3.35 0.5 units box
fix zden7 liq2 ave/chunk 10 10000 100000 cc7 density/mass file liq2.profile ave running
velocity ionic create 580.0 4928459 rot yes mom yes dist gaussian
velocity mysheet create 580.0 4928459 rot no mom no dist gaussian
velocity mysheet zero linear

run 5000000

at 600k

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2.550

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hello users,

I have a mixture consisting two liquids(liq1+liq2)confined between graphite sheets ,initially i run the system at 600k to relax the system and then compute the density using the following commands:once i get the density profile symmetric in this temperature i tried to anneal the system slowly,but still the density profiles are not coming symmetric.is there any thing wrong in the command.I want the system temperature to be 400 K . why the annealing the is not done properly? any suggestions!help!!!

first of all, this seems to be more a question about the science of the problem, than about the chunk commands.
the fact, that you don’t get the result you expect, doesn’t automatically mean, that the commands to analyze are incorrectly used.

have you visualized your simulation?

the density profiles hint, that you have layers formed and no real “bulk liquid” area. so by what mechanism, should there be a significant exchange of molecules in z-direction, which would be a prerequisite for symmetric density distributions? besides, couldn’t it also be possible, that the specific geometries of the two types of molecules favors a specific orientation and stacking next to each other, which in turn could result into a preferred distribution once the symmetry has been broken?

at any rate, i think you can so far assume. that the LAMMPS computations are correct and thus have to think about what the result means.
also, the second part of your simulation seems inconsistent. you reset/rescale the velocities, but then do a temperature ramp down to that value with the thermostat.

axel.

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Thanks a lot! for the suggestion

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