Hello Dear LAMMPS users
I’m trying to simulate quenching process of a shock product. shock product itself is acquired through nphug simulation and has high temperature and pressure. what do you suggest for quenching fix? npt fix causes highly disordered structure and nonphysical behavior and using fix nvt doesn’t give the a rational final press.
I would appreciate your kind help
thanks
Ali
Hello Dear LAMMPS users
I'm trying to simulate quenching process of a shock product. shock product
itself is acquired through nphug simulation and has high temperature and
pressure. what do you suggest for quenching fix? npt fix causes highly
disordered structure and nonphysical behavior and using fix nvt doesn't
give the a rational final press.
the way i learned it, quenching means setting all velocities to zero,
either immediately, or through adding a suitable amount of viscosity. the
former is done with the velocity command, the latter can be achieved with
with fix viscous or (implicitly) through fix langevin.
please note, that nose-hoover thermostats are designed to provide correct
sampling of an equilibrium system, but *not* to remove or add lots of
kinetic energy quickly. you need a rescaling or dissipative thermostat for
that.
axel.
Dear Axel
Thanks for your kind answer …
And thanks again for your advice about thermostats.
Actually my Aim is to obtain the final shock product. Since after the shock we have an amorphous bulk with high temperature and pressure (simulated with hugoniostat method). I need to somehow equilibrate it to reach what we have in experiment and examine the final crystallized or amorphous structure. So we need to solidify the system with a specific cooling rate (in some experimental and simulation papers they use “quenching” for describing the process doi: 10.1016/j.commatsci.2014.12.037.). the problem is that in conventional studies the initial structure is melted in constant pressure (npt) and thus can be solidify with (npt) afterwards, but in my case which I have used nphug fix as I mentioned, for solidification npt fix causes highly disordered structure and nonphysical behavior and using fix nvt doesn’t give a rational final press. Can you suggest me another good method/fix which is more related?
Ali
Dear Axel
Thanks for your kind answer ...
And thanks again for your advice about thermostats.
Actually my Aim is to obtain the final shock product. Since after the
shock we have an amorphous bulk with high temperature and pressure
(simulated with hugoniostat method). I need to somehow equilibrate it to
reach what we have in experiment and examine the final crystallized or
amorphous structure. So we need to solidify the system with a specific
cooling rate (in some experimental and simulation papers they use
“quenching” for describing the process doi: 10.1016/j.commatsci.2014.12.
037.). the problem is that in conventional studies the initial structure
is melted in constant pressure (npt) and thus can be solidify with (npt)
afterwards, but in my case which I have used nphug fix as I mentioned, for
solidification npt fix causes highly disordered structure and nonphysical
behavior and using fix nvt doesn't give a rational final press. Can you
suggest me another good method/fix which is more related?
if you have non-physical behavior, that may be an indication, that you are
doing things incorrectly.
for the rest, i could only repeat the advice that i have already given
before.
axel.