Dear LAMMPS users,
I’d like to perform NEMD simulation of a simple LJ system, applying a xy shear deformation.
Thus, I am using fix deform (enabling remap v) with a Langevin thermostat modified with the temp/deform option. In particular, I use a vel style with velocity 0.1.
In this way, I get a consistent velocity profile (computed with ave/chunk) that goes from 0 to 0.1 across the extension of the y axes.
However, in testing the script, I also tried to run the simulation with
1. no temp/deform option
2. with temp/compute instead of temp/deform
In both these cases, despite the velocity profile is consistent, it is also shifted by a factor of 0.5*vel (it goes from -0.05 to 0.05 across the y axes). What is precisely the reason for this shift? It appears that not using temp/deform enable a shear deformation both in the upper and lower layer of the box in opposite directions. Is this true? And, why is it the case also for temp/compute?
I see that, at least in case 1, I am not making the stream velocity coherent with the box deformation but I don’t understand the reason for this shift.
These are the most relevant commands I am using:
fix thermofix all langevin 0.722 0.722 1.0 12345 zero yes
fix thermofix1 all nve
compute sheartemp all temp/deform
fix_modify thermofix temp sheartemp
fix shearbox all deform 1 xy vel 0.1 remap v flip yes units box
Thank you for your patience.