Dear LAMMPS users,
I am trying to do a radiation damage in a crystal lattice. Due to the high initial energy of the PKA, I am aware that the primary time step will be small, around nearly 1 fs and then it will increase after the PKA loses most of its energy. I am aware that we need to use fix dt/reset to set this variable time step, my question is if I am simulating under NVE ensemble, can I use fix nve/limit instead of using fix dt/reset command?
Thank you in advance…
Best regards
Dear LAMMPS users,
I am trying to do a radiation damage in a crystal lattice. Due to the high
initial energy of the PKA, I am aware that the primary time step will be
small, around nearly 1 fs and then it will increase after the PKA loses
most of its energy. I am aware that we need to use fix dt/reset to set this
variable time step, my question is if I am simulating under NVE ensemble,
can I use fix nve/limit instead of using fix dt/reset command?
fix nve/limit does *not* simulate an NVE ensemble, but arbitrarily slows
down atoms that are moving too fast. thus the resulting trajectory will be
different from one generated with fix nve and unphysical to boot.
if you don't want to use fix dt/reset, you can use fix nve with a suitably
small time step.
mind you, a time step of 1fs is not exactly small for first row element...
what is "small" very much depends on local kinetic energy and mass of atoms.
axel.
Dear LAMMPS users,
I am trying to do a radiation damage in a crystal lattice. Due to the high initial energy of the PKA, I am aware that the primary time step will be small, around nearly 1 fs and then it will increase after the PKA loses most of its energy. I am aware that we need to use fix dt/reset to set this variable time step, my question is if I am simulating under NVE ensemble, can I use fix nve/limit instead of using fix dt/reset command?
As suggested by Axel, the fix dt/reset is THE good way to do it. And 1 fs is indeed usually VERY large for the PKA…
Also, the litterature on irradiation by MD usually mention the maximum atomic displacement that is allowed during one step of dynamics. So follow these indications !
Julien