Hi,
The total energy is not converging in sputtering simulations. I am testing with the LAMMPS example demo file. Please find the attached total energy versus time curve for your reference. Generally, a thermodynamic equilibrium attains at some point in the simulation’s time. It is not happening in these simulations. Any comments on this observation are appreciated.
Please find my input file as follows
surface sputtering demo
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 lj
atom_style atomic
boundary p p f
lattice fcc 0.85
region box block 0.0 {len} 0.0 {len} -1.0 40.0 units lattice
particle density in z-direction is inhomogeneous:
only do domain decomposition in x- and y-direction
processors * * 1
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 1.0
mass 2 3.0
region fixed block INF INF INF INF 0.0 0.1
group fixed region fixed
group mobile subtract all fixed
pair_style lj/cut/opt 2.5
pair_coeff 1 1 1.0 1.0
pair_coeff 2 2 0.5 1.2
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 0.4 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 2000 sputter.xyz
minimal equilibration
run 100
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
deposite particles regularly into insert volume
fix insert insert deposit 50 2 200 12345 region insert vz -8.0 -9.0 &
target {len2} {len2} ${hgt} units lattice
neigh_modify every 1 delay 0 check yes
time integrate inserted particles
fix 4 insert nve
compute ke4 insert ke
remove thermostat on layer atoms
unfix 2
variable nlayer equal count(mobile)+count(fixed)
variable ninsert equal count(insert)
thermo_style custom step atoms v_nlayer v_ninsert temp etotal v_len2 c_ke4
thermo_modify temp mtemp
handling of atoms the get bounced back from surface
or sputtered off the surface.
thermo_modify lost ignore flush yes line multi
run 2000000
with kind regards,
Satya
