pspxc from pseudopotential not equal to ixc

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mverstra
Posts: 655
Joined: Wed Aug 19, 2009 12:01 pm

pspxc from pseudopotential not equal to ixc

Post by mverstra » Wed May 05, 2010 8:04 pm

Abinit complains if the exchange correlation functional (variable ixc http://www.abinit.org/documentation/helpfiles/for-v6.0/input_variables/varbas.html#ixc) used in the input is not the same as that specified in the pseudopotential / atomic data files used.

Code: Select all

 pspatm: WARNING -
  Pseudopotential file pspxc=       7,
  not equal to input ixc=       1.
  These parameters must agree to get the same xc
  in ABINIT code as in psp construction.
  Action : check psp design or input file.
  Assume experienced user. Execution will continue.


This is usually dangerous, as you are making uncontrollable errors in compensating for the Vxc of the core in the pseudopotential with a different functional.

However, there is an important exception: all the LDA functionals (ixc 1-7) are basically identical, but with different functional forms to fit the same data. As a result, mixing these ixc is mostly harmless (as above). The warning appears often, as the many pseudopotentials on the web site are created with a variety of ixc, not necessarily the default value 1.
Matthieu Verstraete
University of Liege, Belgium

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