Apply external electric field to metal atoms

Hello everyone,

I am trying to apply external electric field to a layer of metal atoms using ReaxFF and fix efield. I am new in this field. The problem is when I am applying that field I can not see expected change in charge of atoms in output file (from compute charge) . I do not know why. Do you have any idea what is the problem? This is my input script and attached are geometry and ReaxFF input files.

Thank you in advance,
H. Dormohammadi

dimension 3
boundary p p m
units real

atom_style charge
read_data Ni.dat

create groups

group Ni type 1

region electricfield1 block 0.0 10.50 0.0 12.0 9.0 11.0

group eef region electricfield1

#ReaXFF
pair_style reax/c NULL
pair_coeff * * ffield.reax Ni

neighbor 2 bin
neigh_modify every 10 delay 0 check no

fix 1 all nvt temp 300.0 300.0 1000.0
fix 2 all qeq/reax 1 0.0 10.0 1e-6 reax/c

fix 3 all reax/c/species 1 50 1000 species.out element Ni position 1000 Ni.pos
fix 4 all reax/c/bonds 1000 bonds.reaxc

velocity all create 300.0 4928459 rot yes mom yes

minimize 1.0e-6 1.0e-8 1000 1000

compute charge all property/atom q
dump 102 all custom 1000 dump.charge id type x y z c_charge

thermo 1000
thermo_style custom step temp pe ke etotal

#run variables
timestep 0.10
run 40000

fix 5 eef efield 0.0 0.0 0.6
run 20000

Ni.dat (2.92 KB)

ffield.reax (25.5 KB)

1 Like

Hello everyone,

I am trying to apply external electric field to a layer of metal atoms using
ReaxFF and fix efield. I am new in this field. The problem is when I am
applying that field I can not see expected change in charge of atoms in
output file (from compute charge) . I do not know why. Do you have any idea
what is the problem? This is my input script and attached are geometry and

the explanation is obvious from reading the fix efield documentation.
it very clearly states that what fix efield does is adding a charge
dependent force to atoms. that is a crude empirical approximation to
how charged particles react to an external field. it does *not* in any
form model how an electric field would influence the charge
distribution. the charge equilibration process in reax has no
knowledge of it. technically, there is no electrical field, but just
an added force. if you want to model the reaction of a system modeled
with reaxff under an external electrical field, you have to modify the
reaxff code accordingly in a rather non-trivial manner.

axel.