How to use Fix field command ?

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1

Dear

hi

i have been working on project about seawater desalination by using Lammps

The Key of this project is how many Na and Cl ions are attached to the electrode depending on the intensity of eletric field.

so we used fix field command to Add a force F = qE to each charged atom in the group.

this is our input script file

units real
atom_style full
boundary p p f
lattice sc 1.0

Define force field

pair_style lj/cut/coul/long 10.0 12.0
bond_style harmonic
angle_style harmonic
dihedral_style none
improper_style none
kspace_style pppm 1.0e-4
kspace_modify slab 3.0
read_data data_50NaCl_2746H2O_gra9.17_conc0.990_SC5.txt

neighbor 2.0 bin
neigh_modify every 2 delay 4 check yes

thermo_style custom step temp etotal ke pe epair
thermo_modify flush yes
thermo 100
#minimize 1e-4 1e-6 1000 100000
velocity all create 100.0 3451 dist gaussian loop local

group fluid type 1 2 3 4
group gra type 5

Equilibrate the initial condition

Run first npt, second nvt

timestep 0.001
fix 1 fluid shake 0.0001 20 0 b 1 a 1
fix 2 gra setforce 0.0 0.0 0.0
fix 3 fluid nvt temp 10.0 10.0 50.0 drag 0.2

run 10000
timestep 0.2
run 10000
write_restart restart.init

unfix 3
restart 20000 restart.*

dump 1 all xyz 100 dump0.xyz
dump_modify 1 element Na Cl O H C
fix 4 fluid nvt temp 293 293 100.0 drag 0.2
fix 5 gra efield 0.0 0.0 10.0
timestep 2.0
run 10000 # 2ns equilibration
undump 1

write_restart restart.Eq

dump 2 all xyz 100 dumpEq1.xyz
dump_modify 2 element Na Cl O H C

run 10000 # 2ns production
undump 2
write_restart restart_data1

dump 3 all xyz 100 dumpEq2.xyz
dump_modify 3 element Na Cl O H C

run 10000 # 2ns production
undump 3
write_restart restart_data2

it must have some errors within the input script but we don’t know exactly where it is

Let me say again.

we want to see amount of ions attached to the electrode depending on the intensity of eletric field

so we also want to add various value of eletric force to electrode .

Please tell me any single word if there is something wrong and show me the direction how to add various value of eletric force to electrode .

l’m looking forward to hearing from you

Best regard.

Cheers

Won

University of kwang -Woon Seoul,

Department of Chemical Engineering

Korea

2

Dear

hi

i have been working on project about seawater desalination by using Lammps

The Key of this project is how many Na and Cl ions are attached to theelectrode depending on the intensity of eletric field.

so we used fix field command to Add a force F = qE to each charged atom in
the group.

[...]

it must have some errors within the input script but we
don't know exactly where it is

well, how should anybody else know?
you don't even say why you think there are errors.

Let me say again.

we want to see amount of ions attached to the electrode depending on
the intensity of eletric field

so we also want to add various value of eletric force to electrode

how you define your model is up to you. LAMMPS provides the tools for it
and the individual LAMMPS commands are documented in the manual. also, how
you analyze and interpret your simulation is your job.

so either you have problem with the syntax or a question about how a
specific command works, then you have to ask a more specific question.

or you are looking for a collaborator that works with you to build your
model and is interested in your research, then you have to say so.

axel.