Building an equimolar CoCrFeMnNi in Lammps

LAMMPS LAMMPS General Discussion
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1

Hi,
I want to build an equimolar CoCrFeMnNi (20% at. each) in Lammps. I wrote the script for the tension test. However, when I wanted to visualize it with Ovito, I saw it explode. I tried other combinations, and it works. But it does not work for this specific ratio and keeps exploding. I would be so grateful if there could be a suggestion for that.
with regards,
here is the script:

# ------------ Initialization -------------
units		metal
dimension	3
boundary	p p p
atom_style	atomic
variable latparam equal 3.595

# ------------ Atom Definition ------------
lattice 	fcc ${latparam} orient x 1 0 0 orient y 0 1 0 orient z 0 0 1
region		whole block   0    10    0    10    0   10 
create_box	5 whole

mass 1 58.933195  
mass 2 51.9961    
mass 3 55.845     
mass 4 54.938044  
mass 5 58.6934

create_atoms 3 box

set type 3 type/fraction 1 0.2 12345 
set type 3 type/fraction 2 0.25 54321 
set type 3 type/fraction 4 0.33 11111
set type 3 type/fraction 5 0.5 22222


group g1 type 1
group g2 type 2
group g3 type 3
group g4 type 4
group g5 type 5

dump 1 all custom 100 md.dump id type x y z

minimize 1.0e-4 1.0e-6 100 1000

# ------------ Force Fields ---------------
pair_style	meam
#pair_coeff	* * library.meam Co Cr Fe Mn Ni test.meam.txt Co Cr Fe Mn Ni
pair_coeff	* * library.meam Co Cr Fe Mn Ni CoCrFeMnNi.meam Co Cr Fe Mn Ni

# ------------ Equilibration --------------
#reset_timestep 0
timestep 0.001

delete_atoms overlap 0.3 all all

velocity all create 300 12345 mom yes rot no
#fix 1 all nve
fix 2 all npt temp 300 300 0.1 iso 0 0 1 drag 1

thermo 100
thermo_style custom step lx ly lz press pxx pyy pzz temp

run 4000

write_data equil300kalloy.data

unfix 2

variable tmp equal "lx"
variable L0 equal ${tmp}

variable L1 equal ly
variable L2 equal lz

# ------------ Deformation --------------
fix	2 all nvt temp 300 300 .1

variable srate equal 1.0e10
variable srate1 equal "v_srate / 1.0e12"

fix	3 all deform 1 x erate ${srate1} units box

variable strainx equal "(lx - v_L0)/v_L0"
variable strainy equal "(ly - v_L1)/v_L1"
variable strainz equal "(lz - v_L2)/v_L2"
variable p1 equal "v_strainx"
variable p2 equal "v_strainy"
variable p3 equal "v_strainz"
variable p4 equal "-pxx/10000"
variable p5 equal "-pyy/10000"
variable p6 equal "-pzz/10000"

fix def1 all print 100 "${p1} ${p2} ${p3} ${p4} ${p5} ${p6}" file CoCrFeMnNi_100.def1.txt screen no

thermo 100
thermo_style custom step v_strainx v_strainy v_strainz press temp v_p4 v_p5 v_p6
run 10000

print "All done"
2

Other combinations of what?

If the same input has worked for other materials, then the most likely culprit is the pair_coeff command and the parameter files. Where did you get them from? How did you come to use the exact pair_coeff command line that you chose.

3

Hi,
I mean other atomic ratio for CoCrFeMnNi worked but 20%at. did not.

4

This does not answer my second question.

5

Hi Marya,

Maybe the starting point to solve your problem would be reading the article that your potential is based on. If you got it from the interatomic potential repository, they provide proper reference for their potentials.

6

I used the potential file from here: Interatomic Potentials Repository

7

In the quoted input you are using you have:

pair_coeff * * library.meam Co Cr Fe Mn Ni CoCrFeMnNi.meam Co Cr Fe Mn Ni

But the potential file in the NIST repository is called CoNiCrFeMn.meam and because of the subtleties and rules for MEAM potentials, your input is incorrect and it should instead be:

pair_coeff * * library.meam Co Ni Cr Fe Mn CoNiCrFeMn.meam Co Cr Fe Mn Ni

Any simulation with the same potential must use this input or else the simulation will be bogus.

In addition, you can get a much better match for your composition with
set type/ratio instead of set type/fraction.

8

Awesome. Thank you. It worked. I appreciate your help.
Regards,