Hi everyone, I’m trying to conduct a shear simulation on a bicrystal using velocity command and want to get the shear stress of the mobile area, namely stress_yz. But I got the error massage: “Substitution for illegal variable syz_grain”. I read the manual but still don’t know what was wrong with my code. Could you please tell me how to fix this problem. Here is my code and illustration of the bicrystal. Thanks in advance.

compute peratom all stress/atom new2d

compute vatom all voronoi/atom

#compute vonmises stress

variable sigma_x atom c_peratom[1]/(c_vatom[1]*10000)

variable sigma_y atom c_peratom[2]/(c_vatom[1]*10000)

variable sigma_z atom c_peratom[3]/(c_vatom[1]*10000)

variable sigma_xy atom c_peratom[4]/(c_vatom[1]*10000)

variable sigma_xz atom c_peratom[5]/(c_vatom[1]*10000)

variable sigma_yz atom c_peratom[6]/(c_vatom[1]*10000)

variable vonmises atom sqrt(((v_sigma_x-v_sigma_y)^2+(v_sigma_x-v_sigma_z)^2+(v_sigma_y-v_sigma_z)^2+(v_sigma_xy^2+v_sigma_xz^2+v_sigma_yz^2)*6)/2)

#compute shear stress of mobile area

compute syz_strain mobile reduce sum v_sigma_yz