Dear LAMMPS user,
I have tried using the hybrid potential for Ni and He. I am using 3 different potentials, for Ni-Ni I am using EAM potential, He-He Becks, and for Ni-He I am using Morse potential( parameters for morse are taken from( Jixing Xia, Wangyu Hu, Jianyu yang, Bingyun Ao, and Xiaolin Wang, “A comparative study of helium atom diffusion via an interstitial mechanism in nickel and palladium”, physica status solidi (b) Volume 243, Issue 3, pages 579–583, March 2006)
My question is when I use these three potentials as shown below using fcc structure of nickel with helium is becoming amorphous. Is there any other way that I can make these potentials work? Thank you for your help
units metal
boundary p p p
atom_style atomic
lattice fcc 3.52
region box block 0 10.0 0 10.0 0 10.0
create_box 2 box
create_atoms 1 box
create_atoms 2 random 100 878567 box
pair_style hybrid eam beck 8.0 morse 10.0
pair_coeff 1 1 eam nimib
pair_coeff 2 2 beck 398.67 0.869 0.675 4.390 0.0003746 2.964
pair_coeff 1 2 morse 0.00019 6.46724 2.559
mass 1 58.6934
mass 2 4.002
group Ni type 1
group he type 2
---------- Define Settings ---------------------
compute eng all pe/atom
compute eatoms all reduce sum c_eng
pair_write 1 2 2000 r 1.0 6.0 Ni.txt eam
compute pair all pair/local dist eng force
fix 1 all box/relax aniso 0.0 vmax 0.1
thermo_style custom step pe lx ly lz press pxx pyy pzz c_eatoms vol etotal
thermo 1
---------- Dump coordinates ---------------------
minimize 1.0e-30 1.0e-30 100000 1000000
unfix 1
---------- Run Minimization ---------------------
reset_timestep 0
fix 1 all nve
thermo 100
thermo_style custom step pe lx ly lz press pxx pyy pzz
min_style cg
minimize 1e-30 1e-30 100000 100000
unfix 1
Dear LAMMPS user,
I have tried using the hybrid potential for Ni and He. I am using 3
different potentials, for Ni-Ni I am using EAM potential, He-He Becks, and
for Ni-He I am using Morse potential( parameters for morse are taken from(
Jixing Xia, Wangyu Hu, Jianyu yang, Bingyun Ao, and Xiaolin Wang, “A
comparative study of helium atom diffusion via an interstitial mechanism in
nickel and palladium”, physica status solidi (b) Volume 243, Issue 3, pages
579–583, March 2006)
My question is when I use these three potentials as shown below using fcc
structure of nickel with helium is becoming amorphous. Is there any other
way that I can make these potentials work? Thank you for your help
if you mix and match potentials that have not been parameterized to
work together, then all kinds of bad things can happen.
please note that the kind of hybrid potential setup that you are using
is meant to work well for systems where you have one segment of one
material and another segments of another material and use some
(approximate, pair-wise additive) potential to describe the
inter-segment interaction. that works pretty well for metal-metal
boundaries or metal-molecule interactions or metal-crystal systems. in
your case, you seem to have something more of an alloy, i.e. the
helium atoms are intermixed into the nickel. that will, for instance,
break down the embedding energy part of EAM model, since those helium
atoms should contribute to the embedding energy, but with your hybrid
model they don't. there may be other issues that are not obvious from
your description.
in general, you can only depend on potentials working as expected for
the systems they have been parameterized for. the further you stray
from that, the less you can depend on it functioning as expected.
axel.