Problem depositing Germanium atoms with Tersoff's potential: Scattering and lost of atoms

Dear all,

I am trying to deposit Ge atoms on a 2x1 Si (100) sample with the Tersoff potential. I’ve done the same experiment with the potential of Stillinger Webber without any problems. The only difference is the temperature used, because as Tersoff’s potential overestimates the melting temperature of Si and Ge. In the case of Tersoff I used temperatures between 1200 and 2200 K. The deposition rate is 1 atom every 2500 steps. The time step is 1 fs. The sample was previously created with 12 Si layers. The first 4 layers are fixed, the next 4 are rescaled to the stipulated temperature every 500 steps and the last 4 are free.

The code is:

# ------------------------ INITIALIZATION ----------------------------
processors	12 7 1

units		metal
boundary	p p f
atom_style	atomic
newton		on

# ----------------------- ATOM DEFINITION ----------------------------

read_data data_dep_term

mass            1 28.085e95
mass		2 28.085
mass 		3 28.085
mass            4 72.64

group fixed        type 1
group substrater   type 2
group substrate    type 3
group addatoms     type 4

region  myblock    block   0.0 92.7576 0.0 92.7576 100.00 100.00

# ------------------------ FORCE FIELDS ------------------------------

# Potencial Tersoff

pair_style      tersoff
pair_coeff      * * SiGe.tersoff Si Si Si Ge

neighbor	0.0 bin
neigh_modify	every 1 delay 0 check no

timestep        0.001
run_style	verlet

# ----------------------------------------------------------------------------------

fix             1 all nve
fix             2 fixed setforce 0.0 0.0 0.0

compute temp0 fixed      temp 
compute temp1 substrater temp
compute temp2 substrate  temp

compute vol all voronoi/atom
compute stressat all stress/atom NULL

fix              depGe addatoms deposit 13824  4 2500 65445 region myblock vz -7.0 -7.0  units box

compute temp3 addatoms   temp
compute_modify	temp3  dynamic/dof yes 

#------------ Equilibration

fix              equilib    substrater temp/rescale 500 1464 1464 1.0 1.0

variable        paso equal step

#----Informacion en lammps.out ------------#
thermo_style    custom step atoms temp c_temp0 c_temp1 c_temp2 c_temp3 ke epair etotal press 
thermo_modify   flush yes 
thermo		100

#To obtain Potential energy per atom
compute         poteng all pe/atom

dump            AtomPosVel   all custom 500 sitf.* id type x y z vx vy vz
dump		AtomPosVel1  all custom 50000 pos.* id type x y z c_stressat[1] c_stressat[2] c_stressat[3] c_stressat[4] c_stressat[5] c_stressat[6] c_vol[1] 

restart          50000  restart1 restart2

run             35000000

I’ve used the August 2019 version.

The problem is:

Several Ge atoms undergo scatering once they reach the surface with Tersoff’s potential. What can I do to fix this? Is it unavoidable? Are there certain things that need to be taken into account?

I have tried for different incident energies of Ge particles, the scattering of Ge atoms persists.

I have a short video of the Ge scattering. I can send you the video if you request me it an email at luis.martin.encinar@…9301…


Best regards. (1.99 KB)