problems accrue with relaxation, and the potential is Reax/c

I wanna simulate the tension of materials. Detailed codes are as follow:
#Lammps 3d Al-Al2O3
units real
boundary p p p
atom_style charge
read_data al_al2o3_whole.txt

reax args: hbcut hbnewflag tripflag precision

pair_style reax/c NULL
pair_coeff * * ffield 7 3 7
neigh_modify every 10 delay 0 check no
velocity all create 300 27851123
#fix f1 all temp/rescale 100 300 300 5 1.0
#fix f1 all nve
fix f1 all npt temp 300.0 300.0 100.0 iso 0.0 0.0 1000.0
fix f2 all qeq/reax 1 0.0 10.0 1.0e-6 reax/c

thermo 100
thermo_style custom step temp epair etotal press lx pxx
timestep 1.0
dump d1 all cfg 1000 Al-Al2O3.*.cfg id type xs ys zs id type q
dump_modify d1 element Al O Al
run 5000
The input file which contains positions of atoms and some related stuff is in enclosure.
Some reasonable results had been got by input file mentioned before. I try to recalculate it by potential of Reax/c, while I choose another potential last time. Unexpectedly, some unreasonable results appeared. The detailed messages are as follow:
LAMMPS (2 Apr 2011)
Reading data file …
orthogonal box = (0 0 0) to (129.6 129.6 129.6)
2 by 2 by 4 processor grid
136471 atoms
Setting up run …
Memory usage per processor = 73.4441 Mbytes
Step Temp E_pair TotEng Press Lx Pxx
0 300 -9562750.6 -9440713.3 nan 129.6 nan
100 nan -110742.52 nan nan nan nan
200 nan -110742.52 nan nan nan nan
300 nan -110742.52 nan nan nan nan
400 nan -110742.52 nan nan nan nan
500 nan -110742.52 nan nan nan nan
600 nan -110742.52 nan nan nan nan
700 nan -110742.52 nan nan nan nan
Is that configuration wrong? Any suggestion?

al_al2o3_whole.txt (6.25 MB)

If you are getting NaNs at time 0, then you likely
have a bogus configuration. Forces have gone to INF.


2011/4/9 meihai3166 <[email protected]>:

Also, I believe your Tdamp and Pdamp need to be adjusted… For Al2O3 with reaxC I’m uising Tdamp=1 Pdamp=300. Remember the units are real so time is in femtoseconds.

Shawn P Coleman

University of Arkansas
Mechanical Engineering