Sputter Question

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.



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

nevermind, i can’t believe I asked such a ridiculous question. I found my mistake. Please disregard.