Hello all,
I have doing diffusion simulations with AIREBO potential with Diamond and Hydrogen doped diamond. I have found inconsistent behavior of the simulation box in both diamond with and without hydrogen. After stabilization i set a the temperature about 2000K or 2500K for diffusion purposes, the system envolves well until destabilization shoots the temperature to 1e7 and strong temperature oscillations happens (also pressure oscilations and energy oscilations). The time step sometimes reduces the problem sometimes not and i need to use too small timesteps. It is not only a timestep problem since i found strange atom shocks during the analisys of the sample along the destabilitazion so i think it could be a bug or a potential problem. I have videos and images that show oscillations and shocks.
Does anybody has similar problems or some idea that could be happening?.
Regards!
Diego Delgado Bueno
PD: I attach one input file used (it starts from restart file due to initial stabilization)
read_restart tmp.restart.1010000
neighbor 3.0 bin
neigh_modify delay 5
mass 1 12.0000
mass 2 1.0000
Groups
group Hydro type 2
group Carbon type 1
group Interst id > 4076
Brenner potential
newton on
pair_style airebo 3.0 1 0
pair_coeff * * CH.airebo C H
initial velocities
compute cal1 all temp
compute cal2 Hydro coord/atom 1.4
compute cal3 Hydro temp
compute cal4 Carbon temp
compute cal5 all pe/atom
fixes
fix 1 Carbon nph aniso 0.0 0.0 0.0 0.0 0.0 0.0 100.0 drag 2.0
fix 2 Hydro nph aniso 0.0 0.0 0.0 0.0 0.0 0.0 100.0 drag 2.0
fix 3 all com 500 COM.out
fix 4 all recenter INIT INIT INIT units box
fix 5 all msd 1 diff4.out
fix 30 Hydro msd 1 diff_h1.out
restart 10000 tmp.restart
thermo 1
thermo_modify temp cal1
thermo_style custom step c_cal1 c_cal3 c_cal4 pe etotal press vol
VARIABLES
variable fx1 index 6 8 10 12 14
variable fx2 index 7 9 11 13 15
variable a index 6 7 8 9
variable stp index 0.000002 0.000001 0.000002 0.000002
variable rn index 50000 100000 100000 4000000
variable t1 index 2000.0 2000.0 2000.0 2000.0
variable t2 index 2000.0 2000.0 2000.0 2000.0
Previous fix
fix ${fx1} Carbon nph aniso 0.0 0.0 0.0 0.0 0.0 0.0 100.0 drag 2.0
fix ${fx2} Hydro nph aniso 0.0 0.0 0.0 0.0 0.0 0.0 100.0 drag 2.0
fix 22 Carbon temp/rescale 5 {t1} {t2} 10 0.8
JUMP TO THE MAIN SCRIPT
jump in.brenner.bulk loop
AND HERE THE LOOP
label loop
log log.$a
unfix ${fx1}
unfix ${fx2}
next fx1
next fx2
fix ${fx1} Carbon nph aniso 0.0 0.0 0.0 0.0 0.0 0.0 100.0 drag 2.0
fix ${fx2} Hydro nph aniso 0.0 0.0 0.0 0.0 0.0 0.0 100.0 drag 2.0
IF LAST RUN SELECT DUMP FILES
if $a == 9 then “dump 1 all custom 10 dump.$a tag type c_cal5 x y z”
if $a == 9 then “dump 3 Hydro custom 10 dump.hydro.cst$a tag x y z”
RUN
timestep ${stp}
run ${rn}
Next Variables
next a stp rn t1 t2
jump in.brenner.bulk loop