hello

I am trying to simulate tensile test and calculate stress-strain curve.i applied the below code but the result was weird also the curve was wrong ( the curve was attached).Could anyone give me any possible reason for this?does the compute that used for calculating the stress wrong?

```
I will be grateful to you, if someone can help and suggest solutin.thank you for your consideration
```

#—initialize simulation------

units metal

dimension 3

boundary s s p

atom_style atomic

#----create atoms-----------

read_data data.1473.ageing

#-------- LJ potentials-------------

pair_style eam/alloy

pair_coeff * * Zope-Ti-Al-2003.eam.alloy Ti Al

#----variable–

variable L equal 82.3

variable dy equal 8.23

variable y1 equal -0.0

variable y2 equal {dy}
#-------------region-----
region Lower block INF INF {y1} {y2} INF INF units box
group Lower region Lower
variable y1 equal {L}-{dy}
variable y2 equal {L}

region Upper block INF INF {y1} {y2} INF INF units box

group Upper region Upper

group boundary union Lower Upper

group middle_atoms subtract all boundary

#—Give some initial velocity to all the atoms randomly at a temperature of 0.01K.

velocity all create 300 511124 rot yes mom yes

#—Compute the stress for each atom and sum each component for all atoms.

compute peratom all stress/atom NULL pair virial

compute fy all reduce sum &

c_peratom[1] c_peratom[2] c_peratom[3] &

c_peratom[4] c_peratom[5] c_peratom[6]

compute p all reduce sum c_peratom[1] c_peratom[2] c_peratom[3]

#—Create a variable called sigmavolume that stores the y component of the stress tensor.

variable sigmavolume equal c_fy[2]/vol

#Create a variable called strain, which calculates the strain during the simulation

variable strain equal (ly-v_L)/v_L

#–Create a variable called press that computes the total pressure.

variable press equal -(c_p[1]+c_p[2]+c_p[3])/(3*vol)

#–Definition of the frequency with which the output information is going to be registered and which variables are going to be recorded.

thermo 10000

thermo_style custom step ly vol v_strain v_sigmavolume temp etotal press v_press

fix relax all nvt temp 0.01 0.01 .01

timestep 0.005

run 500

unfix relax

variable upper_vel equal 0.01

fix zeroing_force_on_lower Lower setforce 0.0 0.0 0.0

fix zeroing_force_on_upper Upper setforce 0.0 0.0 0.0

velocity Lower set 0.0 0.0 0.0 units box

velocity Upper set 0.0 ${upper_vel} 0.0 units box

fix fix1 middle_atoms nvt temp 300 300 0.01

fix fix2 boundary nve

dump 1 all atom 100 s-s.in

run 300000

velocity Upper set 0 0 0

run 1000