Charged system IO3-

Question on input files/tags, interpreting output, etc.

Please check whether the answer to your question is given in the VASP online manual or has been discussed in this forum previously!

Moderators: Global Moderator, Moderator

Post Reply
Message
Author
armando_derezende
Newbie
Newbie
Posts: 8
Joined: Wed Jun 10, 2020 5:06 pm

Charged system IO3-

#1 Post by armando_derezende » Wed Jun 29, 2022 10:18 pm

Dear VASP users,

I want to calculate an IO3- molecule. I am using the following tags in the INCAR:
  • SYSTEM = IO3
    NSW = 1000
    LREAL = .FALSE.
    IALGO = 48
    ISMEAR = 0
    IBRION = 1
    ISIF = 2
    NSIM = 1
    ISYM=0
    ENCUT=800
    PREC=Accurate
    EDIFF = 1E-7
    EDIFFG = -1E-5
    IVDW=12
    NELECT=78
    LDIPOL=.TRUE.
    ADDGRID=.TRUE.
The NELECT=78 comes from 53 + 3*8 +1, for iodine, oxygen and negative charge, respectively.
The calculation runs, but the total energy comes out positive. I have a similar structure HIO3 calculated with similar INCAR (without NELECT and LDIPOL tags), that returns reasonable -21 eV as total energy. I also use this energy in formation reactions and have good results. As HIO3 has neutral charge, the problem must be with NELECT and LDIPOL.

What would be a good combination of tags to solve this problem?
My version is vasp.5.4.4

Thank you very much! :)

Best regards,
Armando

The POTCARS I am using are:
  • PAW_PBE I 08Apr2002
    PAW_PBE O 08Apr2002

The POSCAR is:
IO3
1.0
20.0 0.0 0.0
0.0 20.0 0.0
0.0 0.0 20.0
I O
1 3
Direct
0.5000000 0.5000000 0.5000000
0.5103823 0.4853520 0.5900256
0.4093707 0.4920826 0.4877244
0.5145500 0.5902457 0.4915599

fabien_tran1
Global Moderator
Global Moderator
Posts: 316
Joined: Mon Sep 13, 2021 11:02 am

Re: Charged system IO3-

#2 Post by fabien_tran1 » Thu Jun 30, 2022 7:50 am

Hi,

Your value for NELECT is not correct. By default NELECT is the number of valence electrons (the sum of the ZVAL in POTCAR), i.e. the core electrons are not taken into account. NELECT should be 7+3*6+1=26.

armando_derezende
Newbie
Newbie
Posts: 8
Joined: Wed Jun 10, 2020 5:06 pm

Re: Charged system IO3-

#3 Post by armando_derezende » Thu Jun 30, 2022 10:00 pm

Thank you Mr Fabien!

It is working now. Have a nice day.

Post Reply