Dear all,
I use reax potential to run the equilibrium of graphite. However, the structure after running is not reasonable. It deformed dramatic and curved. My script is below:
#-----------------------initialization------------------------
units real
boundary p p p
atom_style charge
pair_style reax/c NULL
#-----------------------structure-----------------------------
read_data data
#-------------------pair interactions------------------------
pair_coeff * * ffield.reax.cho C
neighbor 2.0 bin
neigh_modify delay 10 check yes
mass 1 12
reset_timestep 0
fix 1 all qeq/reax 1 0.0 10.0 1.0e-6 reax/c
#------------------initial relaxation------------------------
fix 2 all box/relax aniso 0.0 vmax 0.001
thermo 10
thermo_style custom step pe lx ly lz press pxx pyy pzz
thermo_modify flush yes
min_style cg
minimize 1e-25 1e-25 5000 10000
unfix 2
#------------------equilibriation----------------------------
reset_timestep 0
timestep 0.01
velocity all create 298 12345 mom yes rot no
fix 3 all npt temp 298 298 1 iso 0 0 1 drag 1
Set thermo output
thermo 1000
thermo_style custom step lx ly lz press pxx pyy pzz pe temp
thermo_modify flush yes
Run for at least 10 picosecond (assuming 1 fs timestep)
run 1000000
unfix 3
The structure image is attached and I don`t know why it happens.
Thank you for your help
Ximeng
Dear all,
I use reax potential to run the equilibrium of graphite. However, the structure after running is not reasonable. It deformed dramatic and curved. My script is below:
[...]
The structure image is attached and I don`t know why it happens.
you are applying a ReaxFF parameterization meant for studying
combustion of small molecules to a bulk system at room temperature.
why *should* this produce something meaningful?
axel.
Thank you for your help Axel,
Could you give me some suggestions on ReaxFF parameterization? I don`t know which parameter is wrong.
Thank you
Ximeng
Axel Kohlmeyer <[email protected]> 于2018年10月22日周一 下午4:40写道：
Thank you for your help Axel,
Could you give me some suggestions on ReaxFF parameterization? I don`t know which parameter is wrong.
please study the papers describing the parameter sets.
there is a database of ReaxFF parameter sets on Adri van Duin's homepage.
axel.
Hi Ximeng,
The attachment is the tersoff force field which I have used for graphene.
Hope this helps if you would like to use this force field to model.
Dezhao
BNC.tersoff_real (4.59 KB)
Thank you for your help Dezhao. I will be happy to have a try.
Ximeng
Ximeng,
You are probably applying some transverse pressure to the sheets causing them to buckle. You might try using “aniso” instead of “iso” in your barostat, since the compressibility of graphite is very different in the in-plane and out-of-plane directions.
I’ve run graphite just fine with the CHO parameters, but you might consider newer versions like:
Goverapet Srinivasan, S.; van Duin, A. C. T.; Ganesh, P. Development of a ReaxFF Potential for Carbon Condensed Phases and Its Application to the Thermal Fragmentation of a Large Fullerene. J. Phys. Chem. A 2015, 119 (4), 571–580.
https://pubs.acs.org/doi/abs/10.1021/jp510274e
The parameters are in the supporting information. (You’ll have to convert them from pdf to txt format)
Thank you.
-Ben
Thank you so much for your help Jensen,
Have a good one,
Ximeng