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Re: [lammps-users] Electric_field
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Re: [lammps-users] Electric_field

From: Axel Kohlmeyer <akohlmey@...24...>
Date: Wed, 2 Aug 2017 19:32:31 -0400

On Wed, Aug 2, 2017 at 1:14 PM, Mohammad Izadi <izadi0511@...1125.....> wrote:

Dear lammps users,


I’m using lammps/reax/c for simulating decomposition of an organic compound under a constant electric field. From outputs (I mean and specie) I recognized that the electric field is worked but I’m not sure that it’s exactly correct or not. Please look into my input file and make recommends if it needs. This is my input file:

​you seem to be confusing the purpose of a mailing list. it is most certainly not an input file approval or debugging/correction service​.
in other words, it is part of the job of a researcher to validate that a chosen model is giving results at the expected level of accuracy and usefulness.

please let me repeat what i have pointed out in an earlier e-mail response. when you are using fix efield, you are not exactly applying an electric field, you are adding a force to all charged atoms, that depends on the product of the (partial) charge of each atom and a given force constant with conversion factor.
this does not include the electric field in the charge equilibration (only indirectly over response to the force generated by fix efield) and there is no screening or other effects taken under consideration.




echo            both

units                real

dimension 3

boundary  p p p

atom_style       charge


#read_restart    restart22

restart 500      restart11 restart22

pair_style         reax/c NULL

pair_coeff        * * ffield.reax.rdx C H O N

compute reax all pair reax/c

variable eb        equal c_reax[1]

variable ea        equal c_reax[2]

variable et         equal c_reax[9]

variable ew       equal c_reax[11]

variable efi       equal c_reax[13]

variable eqeq    equal c_reax[14]

#define a region for efield

region    elecf block 0.0 100.0 0.0 100.0 0.0 100.0 units box

group     elf region elecf

neighbor          2 bin

neigh_modify  every 10 delay 0 check no

velocity        all create 300 235485 mom yes rot yes

fix                    1 all nvt temp 300 300 25    ###########timestep*100=25

fix             2 all qeq/reax 1 0.0 10.0 1e-6 reax/c

fix             3 all reax/c/species 1 50 250 species.txt

fix             4 elf efield 2.0 0.0 0.0 region elecf

fix_modify      4 energy yes

thermo_style    custom   step    atoms   temp   press   vol   etotal   ke   pe   v_eb   v_ea  v_et   v_ew v_efi   v_eqeq

thermo          250

timestep           0.25

dump               1 all atom 30 dump.reax.rdx

dump               2 all xyz  30

run    30000

Thanks in advance  

Mohammad Ebrahim Izadi 

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Dr. Axel Kohlmeyer  akohlmey@...12...24...
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.