ABINIT Discussion Forums

Dear Abiniters, I have a question.

When we do NLO calculations, we have to choose ixc= 3, 7 or 11. But the example in the tutorial uses 13al.pspnc and 33as.pspnc as psp whose ixc should be 1. I did the same thing and a warning is issued that:

===============================================================================================================
pspatm: WARNING -
Pseudopotential file pspxc= 1,
not equal to input ixc= 3.
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.
================================================================================================================

But there is a note in the explanation of the variable ixc:

================================================================================================================
Note that the choice made here should agree with the choice made in generating the original pseudopotential, except for ixc=0 (usually only used for debugging). A warning is issued if this is not the case. However, the choices ixc=1, 2, 3 and 7 are fits to the same data, from Ceperley-Alder, and are rather similar, at least for spin-unpolarized systems.
================================================================================================================

I wondered if we can ignore the warning? Or we have to re-optimize using the psp with ixc=3? And is there any particular psp file fits ixc=3?

Mixing LDAs is not too much of a problem. If you want to make your own, use opium or fhi98pp, or even atompaw, which now includes Libxc and so will be able to generate ixc 3 - you just have to find the correspondence btw ixc 3 and the libxc code

Matthieu