[Wien] Ghostbands appear in Wien2k05 but not in Wien2k03, a problem of bcc Fe ?

[Gerhard Fecher]

I wonder if there was somewhen betwen Wien2k04 and Wien2k05 any change with the QTL-B Ghostband error recognition that was not present in Wien2k03.

The problem is the following and appears in the actuall and some older Versions of Wien2k05:
I tried to optimize Fe, intended to calculate the range of about -8% to +8% of the lattice parameter.
I started with the experimental lattice parameters (2.867A spacegroup 229 for Fe).
I used RMTs being 8% (I tried also 6%) lower than needed for the experimental lattice parameter, otherwise the spheres will later overlap for the "small" lattice parameter.

The calculations stopped with a QTL-B Ghostband error in lapw2 either in the first, but latest in the 3rd scf cycle.
In particular this was the cases for lattice parameters -2% ... -6% (-8%). It is probably interesting to note that the larger lattice parameter worked with the small RMT. The error appears rather fuzzy, sometimes a very small change of the RMT already makes it vanishing, in spin polarized calculations it appears either in lapw2 -up or -dn, just with small changes in the input parameters (unfortunately I did not keep all possibilities I tried in mind)

I also changed the energy values in the in.. files, without healing the problem.
The use of the switch in1new did not help, but leads to another error that one of the files cannot be read (but thats another story). Anyway, in case of the crash in the first cycle it cannot help at all.

I also tried nearly everything reported and suggested in the last year about the Ghostband error, nothing helped really, maybe just for a particular set of the input what points only on some instability. 

I tried also different fortran compilers (different Versions of Intel and Portland Group), computers, and Linux Kernel Versions, so optimization of the code or any bad library do not cause the problem.

Note the errors occure, indeed, if one just tries to do a simple scf cycle, using the same input parameter, without using the optimization script. It appears for spinpolarized as well as non-spinpolarized calculations but interesting to note for Cr it appeared for bcc but not for CsCl structure with 2 different Cr atoms as a practice for an AFM calculation.

However, all this seems not to be the real problem. I was wondering because its usually a practice for our students to optimize Fe, and last year I never experienced any troubles with calculating or optimizing Fe.

I have one old Version (Wien2k03) running on one computer, and with this Version I do not have any problems (it is even possible to use much smaller RMT values without any troubles). 
I recognized that problem first time with one of the first Wien2k05 Versions at the beginning of the year, but did not follow it as I had not enough time and first thought I just made an error during initialization, and with more complicated structures I haven't had the problem, actually, I guess just by chance.

I am already about to change the fortran code and switch of the stop after the error and convert it to a printed warning only, but do not know whether this may cause any other troubles. 

Peter, in case you cannot reproduce the error or if you need more information then let me know, I will ask Hem to prepare and send a complete set of files.

Thanks and Ciao from Mainz
Gerhard


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