uniaxial tensile deformation-negative value of normal stress?

I am performing a uniaxial tensile deformation in the y-direction using fix deform command (erate) and the other two dimensions are kept under zero applied pressure using fix npt commad. The stress values are calculated using compute stress/atom command and dumped using dump command. I find that the in the stress tensor the normal stress is negative (c_1[2]). I unable to locate the error in my code. kindly help me.

few lines of code is below
fix 1 all deform 100 y erate 0.1
fix 2 all npt temp 300.0 300.0 100.0 x 0.0 0.0 1000.0 z 0.0 0.0 1000.0 dilate all
compute 1 all stress/atom
dump 2 all custom 100 dump.stress_atom_uniaxialtensile c_1[1] c_1[2] c_1[3] c_1[4] c_1[5] c_1[6]

If you read the compute stress/atom and compute pressure doc
pages you will see that one is the negative of the other.
Maybe this is just a mis-understanding of how LAMMPS defines
the term you are printing out.

Steve