Dear Lammps users,
I am trying to generate grain boundary in a five elemental alloy, containing elements e.g. Ni, Co, Cr, Fe, and Al with a concentration of 20% each atomic with FCC atomic structure.
I am creating symmetrical tilt grain boundaries in my material using the method mentioned in LAMMPS tutorial. Grains (Upper and lower plain) are getting distorted during minimization.
I also tried to create bicrystal using ATOMSK tool. After creating bi-crystal in ATOMSK, I tried to minimize it in LAMMPS, again the grain boundary got distorted during minimization.
Please suggest me, how to overcome this problem?
Thanks and Regards,
Sandeep Kumar Singh
Research Scholar,
Mechanical and Industrial Engineering Department,
IIT Roorkee
Dear Lammps users,
I am trying to generate grain boundary in a five elemental alloy, containing elements e.g. Ni, Co, Cr, Fe, and Al with a concentration of 20% each atomic with FCC atomic structure.
I am creating symmetrical tilt grain boundaries in my material using the method mentioned in LAMMPS tutorial. Grains (Upper and lower plain) are getting distorted during minimization.
I also tried to create bicrystal using ATOMSK tool. After creating bi-crystal in ATOMSK, I tried to minimize it in LAMMPS, again the grain boundary got distorted during minimization.
Please suggest me, how to overcome this problem?
it is impossible to give specific advice on a vague description.
in general, atoms go where the model “tells them to go”, i.e. because of the forces they experience and that is due to the geometry and the force field and other settings directly or other choices in the input affecting them indirectly. the simplest test you can do is to see whether the boundary you have created is stable as such. e.g. by modeling only one part of the interface between the two grains. you may have created a geometry with an unstable surface that will experience significant reconstruction because of that.
axel.
Hi Axel,
Thanks for your quick response. Sorry for vague description in my earlier mail. This is my input script for your review.:
---------- Initialize Simulation ---------------------
clear
units metal
dimension 3
boundary p p p
atom_style atomic
---------- Create Atomistic Structure ---------------------
lattice fcc 3.524
region whole block 0.000000 105.1136525 -353.1818724 353.1818724 0.000000 112.768 units box
create_box 5 whole
region upper block INF INF 0.000000 353.1818724 INF INF units box
lattice fcc 3.524 orient x 0 9 2 orient y 0 -2 9 orient z 1 0 0
create_atoms 1 region upper
region lower block INF INF -353.1818724 0.000000 INF INF units box
lattice fcc 3.524 orient x 0 -9 2 orient y 0 -2 -9 orient z 1 0 0
create_atoms 1 region lower
group upper type 1
group lower type 1
#Creation of alloy by substitution#
variable fCr equal 20.0
variable fFe equal 20.0
variable fCo equal 20.0
variable fCu equal 20.0
set type 1 type/fraction 2 ((v_fCr+v_fFe+v_fCo+v_fCu)/100.0) 73873645
set type 2 type/fraction 3 ((v_fFe+v_fCo+v_fCu)/(100.0-v_fCr)) 241325235
set type 3 type/fraction 4 ((v_fCo+v_fCu)/(100.0-v_fCr-v_fFe)) 4234234
set type 4 type/fraction 5 (v_fCu/(100.0-v_fCr-v_fFe-v_fCo)) 2344234
group gNi type 1
group gCr type 2
group gFe type 3
group gCu type 4
group gCo type 5
print “type 1 percent: (100.0-v_fCr-v_fFe-v_fCo-v_fCu) vs (count(gNi)/atoms100.0)"
print "type 2 percent: {fCr} vs (count(gCr)/atoms100.0)”
print “type 3 percent: {fFe} vs (count(gFe)/atoms100.0)"
print "type 4 percent: {fCu} vs (count(gCu)/atoms100.0)”
print “type 5 percent: {fCo} vs (count(gCo)/atoms*100.0)”
Hi Axel,
Thanks for your quick response. Sorry for vague description in my earlier mail. This is my input script for your review.:
that doesn’t really help much. there is no single “magical command” that can “fix” the situation so you get the result you want. that is not how science works.
as I already pointed out, you have to first understand why you don’t get the expected behavior and I suggested a first step toward that. it is irrelevant that the same script worked for a different compound.
thus either you can provide (convincing) evidence that some functionality in LAMMPS is not working as expected, or your way of creating the initial geometry or your potential parameters are flawed. figuring that out is part of your research and not something that can be simply answered by looking at your input.
[…]
Two further comments.
The energetics of your boundary will be determined by your 5-element EAM potential. Getting
a potential that is “good” for 2 elements is hard. 5 is very hard.
You can use fix atom/swap in conjunction with occasional energy minimizations to generate structures
that are well-minimized. E.g. fix atom/swap can segregate certain species to the boundary if that
is where they want to be, energetically. Again, the results will depend entirely on your potential.
Steve