Hi Lammps users,
I am calculating the molecular motion of hydrocarbon. The lammps's
result only reflect the splitting,eg the dehydrogenation of
hydrocarbon. And the molecule do not move at all.I want to seek help
from our lammps users. Thanks you for replying my question. 
Here is my code：
# ReaxFF potential for TATB system
# this run is equivalent to reax/in.reax.tatb,
units real
boundary p p p
atom_style full
read_data nu.data
pair_style reax/c NULL safezone 10 mincap 2000
pair_coeff * * ffield.reax C H
#group m1 id 1:38
#group m2 id 39:76
#group m3 id 77:114
#group m4 id 115:152
#group m5 id 153:190
#group m6 id 191:228
#group m7 id 229:266
#group m8 id 267:304
#group m9 id 305:342
#group m10 id 343:380
compute reax all pair reax/c
variable eb equal c_reax[1]
variable ea equal c_reax[2]
variable elp equal c_reax[3]
variable emol equal c_reax[4]
variable ev equal c_reax[5]
variable epen equal c_reax[6]
variable ecoa equal c_reax[7]
variable ehb equal c_reax[8]
variable et equal c_reax[9]
variable eco equal c_reax[10]
variable ew equal c_reax[11]
variable ep equal c_reax[12]
variable efi equal c_reax[13]
variable eqeq equal c_reax[14]
neighbor 2.5 bin
neigh_modify delay 0 every 10 check no
fix 1 all nvt temp 300 800 10
fix 2 all qeq/reax 1 0.0 10.0 1.0e-6 reax/c
fix 3 all reax/c/species 1 1 200 species.tatb
fix 4 all reax/c/bonds 200 bonds.reaxc
#fix 5 m1 drag 12.74 14.65 12.81 10 15
#fix 6 m2 drag 12.74 14.65 12.81 10 15
#fix 7 m3 drag 12.74 14.65 12.81 10 15
#fix 8 m4 drag 12.74 14.65 12.81 10 15
#fix 9 m5 drag 12.74 14.65 12.81 10 15
#fix 10 m6 drag 12.74 14.65 12.81 10 15
#fix 11 m7 drag 12.74 14.65 12.81 10 15
#fix 12 m8 drag 12.74 14.65 12.81 10 15
#fix 13 m9 drag 12.74 14.65 12.81 10 15
#fix 14 m10 drag 12.74 14.65 12.81 10 15
thermo 500
thermo_style custom step temp epair etotal press &
          v_eb v_ea v_elp v_emol v_ev v_epen v_ecoa &
    v_ehb v_et v_eco v_ew v_ep v_efi v_eqeq
timestep 0.1
dump 1 all custom 5000 paho2.lammpstrj id type q xu yu zu ix iy iz element
dump 2 all xyz 5000 paho2.xyz
dump 3 all custom 5000 paho2.lammps id type q xu yu zu ix iy iz
dump_modify 1 element C H
#dump 2 all image 5 image.*.jpg type type &
# axes yes 0.8 0.02 view 60 -30
#dump_modify 2 pad 3
#dump 3 all movie 5 movie.mpg type type &
# axes yes 0.8 0.02 view 60 -30
#dump_modify 3 pad 3
restart 500 coro-oh.restart
run 250000