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Re: [lammps-users] PKA cascade time step
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Re: [lammps-users] PKA cascade time step

From: Axel Kohlmeyer <akohlmey@...24...>
Date: Sat, 16 Dec 2017 14:22:11 -0500

On Sat, Dec 16, 2017 at 9:50 AM, <> wrote:
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.



Thank you in advance...

Best regards 

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Dr. Axel Kohlmeyer  akohlmey@...12...24...
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.