Questions about GGA-tag

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tsanghsiu · #1 Post by **tsanghsiu** » Fri Nov 09, 2007 6:56 pm

Dear all,
I have couple questions about GGA calculation.
1. I would like to do GGA=PE for bulk calculation and my INCAR looks like as follows.

System = bulk calculation
ISTART = 0
ICHARG= 2
ENCUT = 400
ISMEAR = -5
SIGMA = 0.2
LEXCHG = 5
GGA = PE

dynamic:
IBRION = 2
ISIF = 2
NSW = 200

The POTCAR is come from pot_gga.( In the POTCAR, LEXCH = 91.) Am I right?

2. What the LEXCHG and LEXCH standard for?

3. Can I do GGA = PW or LM or PB for calculation? If I can, what the LEXCHG number is for GGA = PW or LM or PB?

Any advice will be appreciated!

#2 Post by **admin** » Mon Nov 12, 2007 11:23 am

please use the PBE POTCAR if you want to use PE XC, you don't have to get the GGA tag in INCAR explicitely then.

tsanghsiu · #3 Post by **tsanghsiu** » Mon Nov 12, 2007 4:07 pm

Dear Sir,
I have checked our POTCAR library and I find that we just have pot and pot_gga. In pot library, the LEXCH = CA in the POTCAR. In pot_gga library, the LEXCH = 91 in the POTCAR. So, we have not the PBE POTCAR in our POTCAR library. Am I right? If so, how can have the PBE POTCAR?

Thanks so much!

#4 Post by **admin** » Wed Nov 21, 2007 11:03 am

the PBE potentials are only available in the PAW -PP data base.

#5 Post by **admin** » Wed Nov 21, 2007 11:07 am

the PBE potentials are only available in the PAW -PP data base.