Metallic Glass Creation

LAMMPS LAMMPS Beginners
1

Hello.
So I am currently trying to create Ni62Nb38 binary metallic glass. When I run my simulation and analyze it in OVITO, I see that as the glass cools down to low temperatures, then atoms cluster together instead of a disarrayed structure. How can I fix this?
Thank you so much for your help and time.

Script:

units lj
dimension 3
boundary p p p
atom_style atomic

region sim_box block -20.0 20.0 -20.0 20.0 -20.0 20.0
create_box 2 sim_box

mass 1 1.0 # Ni
mass 2 1.0 # Nb

create_atoms 1 random 315 22222222 sim_box # Ni
create_atoms 2 random 190 11111111 sim_box # Nb

pair_style lj/cut 2.5
pair_coeff 1 1 1.0 1.0 # Ni-Ni
pair_coeff 2 2 1.75 1.178 # Nb-Nb
pair_coeff 1 2 1.32 1.085 # Ni-Nb

neighbor 2.0 bin
neigh_modify delay 0 every 1 check yes

velocity all create 0.25 12345 loop geom
minimize 1e-7 1e-9 10000 10000

timestep 0.02
thermo 100
dump 1 all atom 1000 dump.the_goat

fix 1 all npt temp 0.25 2.0 0.1 iso 0.001 0.001 5.0
run 400000
unfix 1

fix 1 all npt temp 2.0 2.0 0.1 iso 0.001 0.001 5.0
run 1000000
unfix 1

fix 1 all npt temp 2.0 0.1 0.1 iso 0.001 0.001 5.0
run 1700000
unfix 1

fix 1 all npt temp 0.1 0.1 0.1 iso 0.001 0.001 5.0
run 1000000 # Adjust this to sufficient time for equilibration (10 ns = 1000000 timesteps)
unfix 1

fix 1 all nve
run 3000000 # 30 ns in timesteps of 0.01
unfix 1

run 20000

2

When trying to model an actual material, LJ units are rarely a good idea. It just makes your life difficult.

Also, is a simple Lennard-Jones potential with very short cut-offs a good model for this system (its an actual question, I don’t know your system) ?

Simon

3

Hi Dr. Simon,
I see what you mean about the cut-off distance. I will look to see if that is the problem. I will double check my values and make sure that they are correct. Thank you so much for your advice.

4

Extremely unlikely.

The whole point of multibody potentials is that LJ potentials (and any purely radial potential in general) cannot capture the ground state angular configurations in solid-state materials.

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