lammps/examples/USER/tally/in.stress

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units real
atom_style full
read_data data.spce
pair_style lj/cut/coul/long 12.0 12.0
kspace_style pppm 1.0e-4
pair_coeff 1 1 0.15535 3.166
pair_coeff * 2 0.0000 0.0000
bond_style harmonic
angle_style harmonic
dihedral_style none
improper_style none
bond_coeff 1 1000.00 1.000
angle_coeff 1 100.0 109.47
special_bonds lj/coul 0.0 0.0 1.0
neighbor 2.0 bin
fix 1 all shake 0.0001 20 0 b 1 a 1
fix 2 all nvt temp 300.0 300.0 100.0
# make certain that shake constraints are satisfied
run 0 post no
group one molecule 1 2
# the following section shows equivalences between using the stress/tally compute and other computes and thermo keywords
# compute per atom stress contributions
compute spa all stress/atom NULL pair
compute press all pressure NULL pair
# compute stress contributions from one group with all
compute c1 one stress/tally all
# collect stress contributions from all with all
compute c2 all stress/tally all
compute one one reduce sum c_c1[1] c_c1[2] c_c1[3] c_spa[1] c_spa[2] c_spa[3]
compute red all reduce sum c_spa[1] c_spa[2] c_spa[3] c_c2[1] c_c2[2] c_c2[3]
#
variable spa equal -(c_red[1]+c_red[2]+c_red[3])/(3.0*vol)
variable press equal -(c_red[4]+c_red[5]+c_red[6])/(3.0*vol)
variable one equal (c_one[1]+c_one[2]+c_one[3])/3.0
variable ref equal (c_one[4]+c_one[5]+c_one[6])/3.0
#velocity all create 300 432567 dist uniform
timestep 2.0
thermo_style custom step c_press v_spa v_press v_one v_ref
thermo 10
run 50