[lammps-users] Silicon fracture in mode I

Hi
I am performing a uniaxial test for slit crack in silicon, but I am unable to see fracture behavior on stress-strain curve, but when I visualize with ovito it clear shows brittle fracture. I am pasting my code. Please help me in sorting my errors
Thanks

units metal
dimension 3
#processors * * *
boundary p p p
atom_style atomic
#atom_modify map array

---------- Create Atoms ---------------------

##ATOM DEFINITION
variable latparam equal 5.44
lattice diamond ${latparam} orient x 1 0 0 orient y 0 1 0 orient z 0 0 1
region whole block 0 180 0 63 0 1 units lattice
create_box 1 whole
mass 1 28.0855
create_atoms 1 region whole
#replicate 180 63 1

##---------- Define Interatomic Potential ---------------------

neighbor 2.0 bin
neigh_modify delay 10 check yes
pair_style sw
pair_coeff * * Si.sw Si

#define slit_crack
region a block 488 INF 0 100 INF INF units box
group right region a
group right region a

region fullstrip block INF INF 0 100 INF INF units box
group right region a
group total region fullstrip
group left subtract total right
neigh_modify exclude group right left

------------------------- SETTINGS ---------------------------------

#compute csym all centro/atom fcc
#compute peratom all pe/atom