GW POTCARs vs. ordinary PBE POTCARS, they result in different Total Energies! why?

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hosfa · #1 Post by **hosfa** » Thu Jul 25, 2013 11:14 am

As I mentioned I tried ordinary PBE POTCARs and GW POTCARs for the same phase with identical INCAR and KPOINTS. But the Total energies for the relaxed structure are considerably different.
PBE: -104.1120
GW: -117.7372
Which one is more reliable?

Torbjorn · #2 Post by **Torbjorn** » Fri Jul 26, 2013 8:04 am

None is better, you should get the same physics (=energy differences) out of either of them for anything that does not depend strongly on the conduction band states. This means most normal calculations. Remember that the value of the total energy does not mean much in itself in a code that works with pseudized quantities (set up and run the hydrogen atom to convince yourself of this...), only energy differences are meaningful, so it is vital that you use the same POTCAR's for all calculations where you intend to compare total energies.

hosfa · #3 Post by **hosfa** » Fri Jul 26, 2013 1:37 pm

[quote="energy differences) out of either of them for anything that does not depend strongly on the conduction band states. This means most normal calculations. Remember that the value of the total energy does not mean much in itself in a code that works with pseudized quantities (set up and run the hydrogen atom to convince yourself of this...), only energy differences are meaningful, so it is vital that you use the same POTCAR's for all calculations where you intend to compare total energies. [/quote"]
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Thanks a lot! a very good reply!!!