Dear Lammps experts,
I am studying the impact behavior of a nanoparticle colliding to the similar substrate with a constant velocity. this nanoparticle is ceramic. So, the long range Coulomb interactions between charges must be considered in the pair_style.
the problem is that when the particle moves toward the substrate its velocity is decreased which might be due to the repulsive forces between the charge of particle and substrate. However, lammps doesn’t mention any warning about the charge neutrality of the model at the beginning of the simulation.
So, please let me know how I can solve this problem. actually I have some ideas :
1- by increasing the particle velocity to ensure that the impact velocity of particle upon impact does not change from the considered initial velocity.
2- make sure that the model is charge neutral
any help is highly appreciated.
Best regards,
Bahman Daneshian,
Helmut Schmidt university of Hamburg
LAMMPS does print a warning at the beginning of the system is not charge neutral.
Collision between the nanoparticle and the surface does decrease the velocity of the nanoparticle. This is what is supposed to happen. By enforcing this not to happen is not a reasonable thing to do.
Ray
thank you for your reply. actually, the problem is that velocity does decrease just before the collision when they are very near to each other. So, the collision velocity decreases which is not suppose to happen!
best regards,
I am studying the impact behavior of a nanoparticle colliding to the similar substrate with a constant velocity. this nanoparticle is ceramic. So, the long range Coulomb interactions between charges must be considered in the pair_style.
the problem is that when the particle moves toward the substrate its velocity is decreased which might be due to the repulsive forces between the charge of particle and substrate.
I agree with Ray.
However, lammps doesn't mention any warning about the charge neutrality of the model at the beginning of the simulation.
(? Charge neutrality does not mean all of the atoms are neutral.)
It makes sense that the surface of a ceramic wall would be charged.
(And if the colliding nanoparticle has the same charge, that will
contribute to the repulsion between them.) Apparently you have other
atoms in your system with the opposite charge. As Ray said, LAMMPS
will complain if the sum of the charges of all the atoms is not 0.
thank you for your reply. actually, the problem is that velocity does decrease just before the collision when they are very near to each other. So, the collision velocity decreases which is not suppose to happen!
?
LAMMPS simulates Newton's laws of motion. F=ma. a is always finite.
The velocity will decrease gradually. You will have to do a better
job of explaining the problem you are having. If it seems your
problem is not a LAMMPS problem, people are unlikely to help.
andrew