[Wien] error in Vorb....uporb.def failed

[shamik chakrabarti]

Dear wien2k users,

     We are doing a simulation study of a spinel ferrite having 56
atoms/cell. This ferrite exhibit non-colinear magnetism. However, as a
first approximation we have simulated it in usual version of wien2k with
colinear magnetism.

Our study showed, that even without structural optimization calculated Li
extraction voltage (obtained from change in total energy due to Li
extraction) matches very well with experimental value.

We have done the above calculation with GGA+U approach and it has run
without any trouble.

However, for further accuracy we have first optimize its lattice parameters
and then atomic coordinates. Optimization of atomic coordinates showed
significant changes in the structure. That optimized structure was further
used for voltage and DOS calculation with same GGA+U approach.

This time, after few iterations it showed,

error in vorb....uporb.def failed (we are using same U value here also as
was done earlier)

Do you think that this error might be correlleted with wrong structural
model or is associated with some other technical problem?

Of course we are simulating a non collinear magnetic syetem in a collinear
code, but it has run smoothly before structural optimization and has given
very accurate Li extraction voltage.

So, it may happen that structural optimization without considering
non-colinear magnetism may have eventually has led to a "very wrong"
structure...which is even further away than the actual one. Is it?

Looking forward to your valuable suggestions.

with regards,
-- 
Shamik Chakrabarti
Senior Research Fellow
Dept. of Physics & Meteorology
Material Processing & Solid State Ionics Lab
IIT Kharagpur
Kharagpur 721302
INDIA
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