Inconsistent results for pressure and stress/atom

LAMMPS LAMMPS Beginners
1

Dear all,
I have tried to calculate components of pressure tensor for my structure. I used two different ways to extract the press coefficients:

  1. Recalling pxx, …
variable pxy equal pxy
  1. use stress/atom command
group solvent type 1 2
compute vis solvent stress/atom mytemp
compute visco solvent reduce sum c_vis[1] c_vis[2] c_vis[3] &
                                  c_vis[4] c_vis[5] c_vis[6]

variable pxxcyl equal -(c_visco[1])/(3*5759.532077)

However, they don’t lead to the same results (The viscosity obtained by the second method is 10 times larger than the first method). Is there any normalization for the number of atom need here?
Thanks

solvate.in (4.5 KB)
solvate.data (815.6 KB)

2

This is explained in great detail on the stress/atom doc page. In summary, press and v_press below are numerically equal:

compute peratom all stress/atom NULL
compute p all reduce sum c_peratom[1] c_peratom[2] c_peratom[3]
variable press equal -(c_p[1]+c_p[2]+c_p[3])/(3*vol)
thermo_style custom step temp etotal press v_press