Dear Users,
I’m looking for a piece of advise. I’m preparing a small nanowire for a lammps demostration. The system is formed be ~20.000 atoms, with boundary conditions set as: s s s (i.e. non periodic system). I would like to keep the free surfaces because the final goal is to subject the nanowire to several loading conditions. The nanowire has been thermalized at 0 K using a NVT ensemble to remove excess heat, reaching stable low total energy and internal pressure with small fluctuation around 0 bar, (fix nvt command).
Now I want to heat it up to 300 K. For that I am using a fix nvt command. I am using a heating rate I consider very low (0.001 K per ps - Leading to a run of 300.000 ps to reach 300 K). However, the nanowire is warping. I can reduce the heating rate even more, and just run the simulation for a longer time. However, I would like to know your opinion about the procedure I am following, I hope your suggestions can help me to avoid the warping of the system while is being heat up or to develop a better strategy to set the system up.
Best regards, and thanks a lot.
Hello John,
What material are you running your simulations on? I have been working with metallic nanowires for the past year. Nanowires a very high aspect ration (i.e. length to diameter). So i think you shoud be using the boundary condition p s s (or set one of the other dimension to be periodic) instead of s s s. I have been using the nvt ensemble routinely for the nanowire without running into any trouble.
Dear Users,
I'm looking for a piece of advise. I'm preparing a small nanowire for a
lammps demostration. The system is formed be ~20.000 atoms, with boundary
conditions set as: s s s (i.e. non periodic system). I would like to keep
the free surfaces because the final goal is to subject the nanowire to
several loading conditions. The nanowire has been thermalized at 0 K using a
NVT ensemble to remove excess heat, reaching stable low total energy and
internal pressure with small fluctuation around 0 bar, (fix nvt command).
Now I want to heat it up to 300 K. For that I am using a fix nvt command. I
am using a heating rate I consider very low (0.001 K per ps - Leading to a
run of 300.000 ps to reach 300 K). However, the nanowire is warping. I can
reduce the heating rate even more, and just run the simulation for a longer
time. However, I would like to know your opinion about the procedure I am
following, I hope your suggestions can help me to avoid the warping of the
system while is being heat up or to develop a better strategy to set the
system up.
how about you define a group for small block of atoms at each end of
the wire and then use fix spring/self to keep it stretched? you
probably want to leave the direction of the wire unrestrained to allow
for expansion
axel.