Hello. I’ve just started my undergrad research and I have some difficulties using meam simulation. Basically I’m trying to create a polycrystal, damage it, then measure the modulus. The attached files are the following: 1 - create the crystal, perform minimization; 2 - damage the lattice by shooting an atom into it; 3 - stress the crystall to create stress-strain plot from dumped data.
The problems I had are the following:
a. In the second simulation (in.meam.SiLiHe) the atom doesn’t travel as far inside the crystall as I expected. Sometimes it creates bonds (that I can see in VMD) with atoms in crystal (I’m not sure how much it affects the physics).
b. In the third simulation (in.meam.SiLiHe.stressed) When I apply force to the crystal (which seems pretty small), the crystal streches (or compresses) with acceleration. I expect the stress to grow inside the crystal and stop straining but it seems quite the opposite. Also, if I apply zero force on it, the total energy grows with time as well as temperature unless I apply thermostatting or minimization.
Please point me at the right direction.
in.meam.SiB (1.33 KB)
in.meam.SiLiHe (703 Bytes)
in.meam.SiLiHe.stressed (642 Bytes)
SiB.meam (202 Bytes)
Your simulations are complex and you are asking hi-level questions.
I doubt anyone is going to sift thru your input scripts to try to
figure things out. You need to ask a more specific question if
you think LAMMPS is doing something unexpected.
Steve
Hello. I've just started my undergrad research and I have some difficulties
using meam simulation. Basically I'm trying to create a polycrystal, damage
it, then measure the modulus. The attached files are the following: 1 -
create the crystal, perform minimization; 2 - damage the lattice by shooting
an atom into it; 3 - stress the crystall to create stress-strain plot from
dumped data.
The problems I had are the following:
a. In the second simulation (in.meam.SiLiHe) the atom doesn't travel as far
inside the crystall as I expected. Sometimes it creates bonds (that I can
see in VMD) with atoms in crystal (I'm not sure how much it affects the
physics).
whatever VMD shows you has nothing to do with the physics
(or rather chemistry) of your system. VMD has *no* chemical
knowledge *at all*. it makes some guesses about your atoms
and then shows bonds, if atom distances are below a threshold
based on those guesses. those can be very wrong unless you
provide VMD with accurate information.
axel.