[lammps-users] Can I specify boundary velocity to be constant? how can I do that

Dear All Developers/Users,

May I know, how to specify the displacement boundary conditions in lammps.
I need to conduct a uniaxial compression/tensile simulation, with the ends of the specimen moving with prescribed velocity in the uniaxial direction, and without constraining the lateral movement of the atoms.

I have tried the fix_deform but I am not satisfied because it uniformly rescales the atoms in the interior.

I found the documentation of fix_deform also is not clear and it is not given clearly about the boundary conditions.
In few of the questions in this form I found a command known as fix_uniaxial, but I don’t find it in the latest version nor in the documentation. Can I know how to use that command and whether that feature is still present in LAMMPS

Please help me.

Thank you,


You can set the velocity of those atoms with the velocity command.
Turn off force on them via fix setforce. Then they will move as
you wish when integrated.