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Trouble shooting

In this chapter hints are given for solving some difficulties that have occurred frequently. This chapter is by no means complete and the authors would appreciate further suggestions which might be useful for other users. Beside the printed version of the users guide an online ASCII version is available using help_lapw. You can search for a specific keyword (use $^{\wedge}$S keyword) and hopefully find some information.

There is a mailing list for WIEN related questions. To subscribe to this list send mail to:
majordomo@zeus.theochem.tuwien.ac.at
with the text ``subscribe wien''.
You will then automatically be added to the mailing list
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Please make use of this list!

If an error occurs in one of the SCF programs, a file program.error is created and an error message is printed into these files. The run_lapw script checks for these files and will automatically stop if a non-empty error file occurs.

Check the files case.dayfile (which is written by init_lapw and run_lapw), :log (where a history of all commands using x is given) and *.error for possible explanations.

In several places the dimensions are checked. The programs print a descriptive error message and stop.

case.outputnn:
This file gives error messages if the atomic spheres overlap. But it should also be used to check the distances between the atoms and the coordination number (same distance). If inconsistencies exists, your case.struct file may contain an error. A check for overlapping spheres is also included in mixer and lapw1.

case.outputd:
Possible stops or warnings are:

``NO SYMMETRY OPERATION FOUND IN ROTDEF``:
This indicates that in your case.struct file either the positions of equivalent atoms are not specified correctly (only positive coordinates allowed!!) or the symmetry operations are wrong.

case.output1:
Possible stops or warnings are:

``NO ENERGY LIMITS FOUND IN SELECT``:
This indicates that Etop or Ebottom could not be found for some ul(r,El). Check your input if it happens in the zeroth iteration. Later, (usually in the second to sixth iteration) it may indicate that in your SCF cycle something went wrong and you are using a crazy potential. Usually it means that mixing was too big and large charge fluctuations occured. Check previous charges for being physically reasonable (grep for labels :NTOxx :CTOxx :DIS). You will probalby have to delete case.broy* and case.scf, rerun x dstart and reduce the mixing parameter in case.inm (In very difficult (magnetic) cases a PRATT mixing with 0.01 mixing might be necessary at the beginning!)

``STOP RDC_22``:
This indicates that the overlap matrix is not positive definite. This usually happens if your case.struct file has some error in the structure or if you have an (almost) linear dependent basis, which can happen for large RKMAX values and/or if you are using very different (extremely small and large) sphere radii RMT.

``X EIGENVALUES BELOW THE ENERGY emin``:
This indicates that X eigenvalues were found below emin. Emin is set in the first line of the k-list (either in case.in (see sec. 7.2.3) or in case.klist generated by KGEN, see 6.3, 6.4). It may indicate that your value of emin is too high or the possibility of ghostbands, but it can also be intentional to truncate some of the low lying eigenvalues.

If you don't find enough eigenvalues (e.g.: in a cell with 4 oxygens you expect 4 oxygen s bands at roughly -1 Ry) check the energy window (given at the end of the first k-point in case.in1 or in case.klist) and make sure your energy parameters are found by subroutine SELECT or set them by hand at a reasonable value.

case.output2:
Possible stops or warnings are:

``CANNOT BE FOUND``:
This warning, which could produce a very long output file, indicates that some reciprocal K-vector would be requested (through the k-vector list of lapw1), but was not present in the list of the K generated in lapw2. You may have to increase the NWAV, and/or KMAXx parameters in lapw2 or increase GMAX in case.in2. The problems could also arise from wrong symmetry operations or a wrong structure in case.struct.

``QTL-B VALUE``:
If larger than a few percent, this indicates appearance of ghost bands, which are discussed below in section 12.1.
The few percent message (e.g up to 10 %) does not indicate a ghost band, but can happen e.g. in narrow d-bands, where the linearization reaches its limits. In these cases one can add a local orbital to improve the flexibility of the basis set. (Put one energy near the top and the other near the bottom of the valence band, see section 7.2.3).
FERMI LEVEL not converged
(or similar messages). This can have several reasons: i) Try a different Fermi-Method (change TETRA to GAUSS or TEMP in case.in2). ii) Count in case.output1 the number of eigenvalues and compare them with the number of valence electrons. If there are too few eigenvalues either increase EMAX in case.klist (from 1.5 to e.g. 2.5) or check if your scf cycle had large charge oszillations (see SELECT error above)

If the SCF cycle stops somewhere (especially in the first few iterations), it is quite possible, that the source of the error is actually in a previous part of the cycle or even in a previous (e.g. the zeroth) iteration. Check in the case.scf file previous charges, eigenvalues, ...whether they are physically reasonable (see SELECT error above).



 
next up previous contents
Next: Ghost bands Up: Installation of the package Previous: Environment Variables

2000-04-11