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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
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
wien@zeus.theochem.tuwien.ac.at
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: Ghost bands
Up: Installation of the package
Previous: Environment Variables
2000-04-11