dear Lammps users, I’m trying to simulate the compression test on my atomic box and then extract stress-strain data to plotting them. I’m facing the mentioned error in topic while running this program:
units metal
echo both
atom_style atomic
dimension 3
boundary s p s
read_restart restart.rejuvenated&relaxed10(10)
timestep 0.002
pair_style eam/alloy
pair_coeff * * CuZrAl.eam.eam Zr Cu Al
energy minimization
minimize 1.0e-9 1.0e-6 1000 1000
compute 1 all stress/atom NULL
compute csym all centro/atom fcc
compute peratom all pe/atom
variable tmp equal ly
variable lo equal ${tmp}
variable strain equal (ly-v_lo)/v_lo
variable p1 equal “-pxx/10000”
variable p2 equal “-pyy/10000”
variable p3 equal “-pzz/10000”
variable p12 equal “-pxy/10000”
variable p23 equal “-pyz/10000”
variable p13 equal “-pxz/10000”
variable fm equal “(v_p1+v_p2+v_p3)/3” #hydrostatic stress
variable fv equal “sqrt(((v_p2-v_p3)^2+(v_p3-Vp1)^2+(v_p1-v_p2)^2+6*(v_p12^2+v_p23^2+v_p13^2))/2)” #von misess stress
variable t equal “v_fm/v_fv”
variable fd equal (((v_p1-v_fm)(v_p2-v_fm)(v_p3-v_fm))-(v_p12)^2*(v_p3-v_fm)-(v_p13)^2*(v_p2-v_fm)-(v_p23)^2(v_p1-v_fm)+2v_p12v_p23*v_p13)#deviatoric von misess stress
#principal stresses
variable I1 equal “(v_p1+v_p2+v_p3)”
variable I2 equal “((v_p1)(v_p2))+((v_p2)(v_p3))+((v_p1)(v_p3))-(v_p12)^2-(v_p23)^2-(v_p13)^2"
variable I3 equal "((v_p1)(v_p2)(v_p3))-((v_p1)((v_p23)^2))-((v_p2)((v_p13)^2))-((v_p3)((v_p12)^2))+2*(v_p12)(v_p23)(v_p13)”
variable A equal “(acos(((2v_I1)^3)-9(v_I1)(v_I2)+27(v_I3))/(2*((v_I1)^2-(3*(v_I2)))^(3/2))))/3”
variable s1 equal “((v_I1)/3)+(2/3)(sqrt((v_I1)^2-(3(v_I2))))cos(v_A)"
variable s2 equal "((v_I1)/3)+(2/3)(sqrt((v_I1)^2-(3*(v_I2))))cos(v_A)-(2PI)/3)”
variable s3 equal “((v_I1)/3)+(2/3)(sqrt((v_I1)^2-(3(v_I2))))cos(v_A)-(4PI)/3)”
thermo 10000
thermo_style custom step temp vol press pe ke etotal
dump 1 all custom 10000 tension_CuZrAl.lammpstrj id
dump 2 all cfg 10000 dump.tensile_CuZrAl*.cfg mass type xs ys zs c_csym c_peratom
dump 3 all custom 10000 stress_peratom.*id type c_1[1] c_1[2] c_1[3] c_1[4] c_1[5] c_1[6]
log NVTlog46468_compressure_CuZrAl.data
velocity all create 300 8175447 rot yes mom yes dist gaussian
#temperature controller
fix 1 all nvt temp 300 300 0.1
#tensile deformation
fix 2 all deform 1 y erate -0.00001 units box
fix 3 all print 10000 “{strain} {p2}” file stress_strain_data.txt
run 1000000
run time error is: Arccos of invalid value in variable formula (…/variable.cpp:3373)
please guide me to solve it