dear all users;
im kind of new to lammps software. im planing to model a graphene under compression at high temperatures, sadly the sheet starts to show up waves.
ive read Dave Schall from the mailing list said "Either that or put in a fix to zero the COM velocity in z so it doesn't drift" . can anyone pls guide me how to do this?
i mean setting fix to a COM.
thanks in advance
dear all users;
im kind of new to lammps software. im planing to model a graphene under
compression at high temperatures, sadly the sheet starts to show up waves.
ive read Dave Schall from the mailing list said "Either that or put in a
fix to zero the COM velocity in z so it doesn't drift" . can anyone pls
guide me how to do this?
you seem to be confusing two issues here: 1) your sheet buckling and 2)
your sheet drifting.
there are multiple ways to go about a center of mass drift:
- fix momentum will remove a developing center of mass momentum. this
requires carefully chosen parameters to avoid unphysical manipulations and
interfering with energy conservation.
- fix spring in tether mode will apply a weak tether (for a proper force
constant), which - depending on the choice of force constant - will have
very little impact on the dynamic, but it may not keep the center of mass
in place, but rather have it oscillate around the tether point.
- you can exclude a few atoms from time integration
to avoid the buckling, a more significant manipulation of the system is
required and thus you have to ask yourself how physically meaningful the
resulting data is going to be.
you can achieve this, for example, via setting velocities (with the
velocity command) and forces (via fix setforce) to zero for all
z-components of velocity and force. without velocity and force, atoms
cannot move.
axel.