[Wien] R0 for atom -3 Z= 33.00 too big

[Jakob Kanter]

Dear Prof. Blaha, dear Wien2K community,

we are running into problems trying to calculate the Fermi surface
of CsFe2As2.

Executing "lstart 13 -6.0" results in:
"WARNING: R0 for atom -3 Z= 33.00 too big".
Suggesting to lower RMT or increase the core-separation energy.

With the RMT values generated by StructGen we find charges outside
the core of

Cs: 9.1e-5 (out of a total core charge of 36)
Fe: 2.0e-3 (out of 12)
As: 2.0e-3 (out of 18)

Increasing the RMT for As lowers the "charge outside sphere" to 1.6e-3 but
does not help the warning message issue.

Cranking the core-separation energy all the way down to -10 Ry changes
the last core state orbital of As from 3P to 3P* and reduces the
"charge outside sphere" to 5e-4 but the warning remains.

I.e. changing RMT and the core separation energy over the whole parameter
range doesn't affect the warning.

Looking at the CsFe2As2.struct file file, it occurs that R0 is 10 times
larger for As compared to Cs and Fe (0.001 vs. 0.00001) but
lowering this value in the struct file causes nn  to act up.

Ignoring the warning the calculation leads to a Fermi surface which
is obviously wrong as it is not symmetric under inversion of k.

Our questions would be:

1) Should R0 be edited directly in the struct file? (probably not)

2) Is the charge leaking out of the MT really the problem? (the charges
    seemed rather small and were in fact bigger for Fe, but the warning
    occurred for As). If so, should we try to force the highest
    core states into valence states by putting an extra LO for that state?
    Are there some issues / stumbling blocks to be considered?

We are running Wien2K v11.1, compiled with ifort v12.0.3
(Intel Fortran Composer XE for Linux 2011.3-174) on a
Intel i7-960 system.

Please find the struct file attached.

Thank you for your time and with best regards,

Jakob Kanter

-- 

_________________________________________

ETH Zurich
Jakob Kanter
PhD Student
Laboratory for Solid State Physics
HPF F 11
Schafmattstrasse 16
8093 Zurich
Switzerland

Phone: +41 44 633 22 47
Fax: +41 44 633 10 72



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