LAMMPS users,
I have a question about the sputtering process in LAMMPS. I am using the sputtering example as a guideline to set up my own sputtering simulation. I created an aluminum FCC crystal. Whenever I try to give an incident Al ion an energy of say, 500 eV and send it to the surface, the aluminum atom does not seem to interact with the bulk material at all. It goes right through the material.
I have reduced my timestep to extremely low values, such as on the order of 10^-7 fs. I cannot figure out why the incident atom just goes right through the material. I have defined the force interactions for the atoms, and am using NVE ensemble to integrate the equations of motion. Any ideas why I might see this?
My script is below.
Thanks,
Ben
surface sputtering demo
package gpu 1 neigh no
suffix off
dimension variables
box length in x and y
variable len index 20.0
height of layer
variable hgt index 8.0
delta between insert area and box
variable len0 index 0.1
full length minus delta
variable len1 equal {len}-{len0}
half length
variable len2 equal ${len}*0.5
units metal
atom_style atomic
boundary p p f
timestep 0.0005
lattice fcc 4.0495
region box block 0.0 {len} 0.0 {len} -1.0 40.0 units lattice
two atom types: surface and sputter atoms
create_box 2 box
region layer block 0.0 {len} 0.0 {len} 0.0 ${hgt}
create_atoms 1 region layer
mass 1 26.981539
region fixed block INF INF INF INF 0.0 0.1
group fixed region fixed
group mobile subtract all fixed
pair_style eam/alloy
pair_coeff * * …/Al_zope.eam.alloy Al Al
neighbor 0.3 bin
neigh_modify every 2 delay 6 check yes
minimize 1.0e-5 1.0e-8 1000 10000
reset_timestep 0
velocity mobile create 300 87287
use the temperature of the mobile layer atoms as reference
compute mtemp mobile temp
fix 1 mobile nve
fix 2 mobile langevin 0.2 0.2 5.0 982434
fix_modify 2 temp mtemp
thermo 100
thermo_style custom step atoms temp etotal
thermo_modify temp mtemp
dump id all xyz 500 sputter.xyz
minimal equilibration
run 1000
define region for inserting particles
region sphere sphere {len2} {len2} 42.0 ${len2} units lattice
region insert intersect 2 box sphere
define group of inserted particles
group insert region insert
fix insert insert deposit 1 2 5 12345 region insert vz -597.994641 -597.994641 &
target {len2} {len2} ${hgt} units lattice
neigh_modify every 1 delay 0 check yes
time integrate inserted particles
fix 4 insert nve
remove thermostat on layer atoms
unfix 2
variable nlayer equal count(mobile)+count(fixed)
variable ninsert equal count(insert)
thermo_modify temp mtemp
handling of atoms the get bounced back from surface
or sputtered off the surface.
thermo_modify lost ignore
thermo 500
fix 100 all dt/reset 1 NULL 0.001 0.01 units box
thermo_style custom step atoms v_nlayer v_ninsert temp etotal time dt
run 1000000