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lammps/examples/USER/atc/fluids/in.opp_force
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in.opp_force
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# Tests Poisson solver, charge density restriction
# and electric field force prolongation
# Two groups of charged particles interact electrically
# using the long range electric field only, so they will
# move towards each other
echo both
units metal
variable E equal 20.0
variable nx equal 16
# allow charges
atom_style full
dielectric 1.
dimension 3
boundary p p p
lattice fcc 4.08 origin 0.25 0.25 0.25
region BOX block -8 8 0 3 0 3
create_box 3 BOX
create_atoms 1 region BOX
pair_style lj/cut 10.
#pair_style lj/cut/coul/long 10.
#kspace_style pppm 1.e-4
#kspace_style ewald 1.e-4
pair_coeff * * 0.2381 3.405
mass * 39.948
group real region BOX
region LEFT block -5 -2 INF INF INF INF
region RIGHT block 2 5 INF INF INF INF
set region LEFT type 2
set region RIGHT type 3
set region LEFT charge -1.
set region RIGHT charge 1.
group NION region LEFT
group PION region RIGHT
neighbor 2. bin
###########################################################################
#fix EFIELD all efield $E 0.0 0.0
###########################################################################
fix ATC real atc species_electrostatic Ar_species.mat
fix_modify ATC add_species N group NION
fix_modify ATC add_species P group PION
fix_modify ATC include atomic_charge
fix_modify ATC internal_quadrature off
fix_modify ATC extrinsic short_range off
fix_modify ATC mesh create ${nx} 1 1 BOX p p p
fix_modify ATC atom_element_map eulerian 1
fix_modify ATC atom_weight multiscale
fix_modify ATC initial mass_density all 0.
#fix_modify ATC initial charge_density all 0.
fix_modify ATC initial electric_potential all 0.
fix_modify ATC mesh create_nodeset left_end -8.01 -7.99 -.1 .1 -.1 .1
fix_modify ATC fix electric_potential left_end 0.
#fix_modify ATC mesh create_nodeset right_end 7.99 8.01 -.1 .1 -.1 .1
#fix_modify ATC fix electric_potential right_end 0.
# quick test for charged surfaces
#fix_modify ATC mesh create_faceset left_end box -8 10 -10 10 -10 10 outward
#fix_modify ATC extrinsic fix_charge left_end 0.
fix_modify ATC add_species NION type 2
fix_modify ATC add_species PION type 3
###########################################################################
variable n equal count(real)
print "number of atoms: $n"
timestep 0.0005
thermo 100
compute Fn NION reduce sum fx
compute Fp PION reduce sum fx
thermo_style custom step etotal temp press pe c_Fn c_Fp
# initial thermo line should be:
#0 13699.992 0 12453927 13699.992 880.49388 -880.49388
fix_modify ATC output opp_forceFE 100 text binary
run 1000
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