[Wien] Strange discontinuity for GGA calculations

[Peter Blaha]

Sorry, but I cannot reproduce your results.

With good parameters I get nice and smooth curves.
The lattice parameter (PBE) is near 8.73, which is smaller
than in your plots.
The RMT dependency is quite small, provided you use good parameters:

RKmax=10 (9 is probably almost ok)
NUMK: I used 11000 (22x22x22) points in full-BZ.(16x16x16 leads to some noise)
Most important for GGA calculations: You have to use a VERY good FFT mesh for
the xc-energy, in particular for smaller spheres. I used IFFT 5 (instead of
the default 2) in case.in0

I attach some plots.


Am 07.09.2010 04:58, schrieb Natalie Holzwarth:
> Dear Wien2k mailing list,
>       For many years, we have been using the wien2k code as a standard for
> comparing our PAW calculations.   Recently, we noticed some difficulties
> particularly with GGA calculations.  The attached example is for Sc in an
> fcc structure using what we think are well converged parameters
> (RMT*KMAX=9, GMAX=14, 16x16x16 kpoints).  We calculate the total energy
> versus lattice constant both for lda and gga varying RMT to make sure that
> there is no sensitivity to the linear LAPW/APW parameters.  RMT = 2.0,
> 1.6, and 1.5 for lda/gga, lda1/gga1, and lda2/gga2, respectively.  The
> binding energy curves are identical for the 3 lda calculations.  But for
> the gga calculations, there seems to be a very strange discontinuity at
> the lattice constant of 9.0 which is very sensitive to the choice of RMT.
> The Sc.in1 file that we used for gga is attached and was obtained from
> running lstart.  Of course I will be very embarrassed if there is a typo
> in our files, but we have not been able to discover it for several days.
> Any advice will be very much appreciated.    Thanks, kindly,
>                                  Natalie Holzwarth
>
> N. A. W. Holzwarth			email: natalie at wfu.edu
> Department of Physics			www: http://www.wfu.edu/~natalie
> Wake Forest University		        voice: 336-758-5510
> Winston-Salem, NC 27109-7507            fax: 336-758-6142
> U. S. A.
>
>
>
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> Wien at zeus.theochem.tuwien.ac.at
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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