running lammps with charged system.

Dear LAMMPS USERS

I am trying to calculate the thermo-physical properties of UO2 with vacancies and interstitial. When we calculate the thermo-physical properties of defected system , how we will take care of the charges arising from the introduction of defects ?. I have few queries.

  1. I saw one of the discussion of Axel in lammps forum (http://sourceforge.net/p/lammps/mailman/message/28496032/),
    there he is giving three options for simulating a charged system. If i adopt the third option i will have either excess/deficient charges in my system. will it affect the thermal properties ?.

  2. One strategy adopted in earlier simulation with pair potential is that, randomly replace U4+ ions with U3+/U5+ to maintain the charge neutrality. Whether I can adopt the same strategy for many body potentials ?. For example if i remove 10 oxygen atom(charge =-1.1104) in UO2, can i replace 10 U atom (charge=2.2208) with charges (2.2208-1.1104=1.1104), to maintain the charge neutrality ?

  3. Another strategy you adopted is that , use a neutralizing jellium. How to add neutralizing ions in lammps simulations.

Please comment over this

Anees p

P.hD student,
HBNI, India

Dear LAMMPS USERS

I am trying to calculate the thermo-physical properties of UO2 with
vacancies and interstitial. When we calculate the thermo-physical
properties of defected system , how we will take care of the charges
arising from the introduction of defects ?. I have few queries.

1. I saw one of the discussion of Axel in lammps forum
(http://sourceforge.net/p/lammps/mailman/message/28496032/),
there he is giving three options for simulating a charged system. If i
adopt the third option i will have either excess/deficient charges in my
system. will it affect the thermal properties ?.

nobody will know that up front.

2. One strategy adopted in earlier simulation with pair potential is that,
randomly replace U4+ ions with U3+/U5+ to maintain the charge neutrality.
Whether I can adopt the same strategy for many body potentials ?. For
example if i remove 10 oxygen atom(charge =-1.1104) in UO2, can i replace
10 U atom (charge=2.2208) with charges (2.2208-1.1104=1.1104), to maintain
the charge neutrality ?

the question is where and how this would be done? this is more a
question of the model you use. nobody can tell you in general.

3. Another strategy you adopted is that , use a neutralizing jellium. How to
add neutralizing ions in lammps simulations.

please read my e-mail from the mailing list carefully. you already
have an answer to that.

axel.

You may find more details when it comes to non-neutral systems by reviewing the derivation of the Ewald technique.

http://protomol.sourceforge.net/ewald.pdf

Carlos