[Wien] about write_in1_lapw

Björn Hülsen huelsen at fhi-berlin.mpg.de
Thu Nov 9 09:47:05 CET 2006

Dear Wien2k developers,

a few days ago I encountered some problems with large differences of the 
hyper fine field for the same input files on different platforms. ( 
http://zeus.theochem.tuwien.ac.at/pipermail/wien/2006-November/008228.html )
The reason for the strange behavior could be tracked down to a different 
functionality of the program "bc" that is used in the write_in1 script. 
According to the support team of the Rechenzentrum Garching the current 
version of the script relies on enhanced features of "bc" that are only 
available in the GNU version but that are not compliant with the 
standard "bc" on the AIX system (and Solaris, IRIX, maybe others).
The query

 if (  `echo "$es < $etest" | bc` == 1 ) then

uses the fact that the GNU "bc" answers with a 1 or 0, respectively. 
With the general "bc" this gives a syntax error that does not lead to a 
crash but also does not switch on the search for the low lying local 
orbitals. So this new feature does not work on the AIX.
A more general version of this query is

 if (  `echo "if ( $es < $etest ) 1" | bc` == 1 ) then

which works with both the general and the GNU "bc". So I suggest to 
include the more general version in the next release of Wien2k.

By the way, when I looked into write_in1, I made a change that if the 
energy of a local orbital is below -3 Ryd and the search for this state 
is switched on, then the CONT is replaced with a STOP like in 
case.in1_orig. Since these local orbitals are really important for the 
scf cycle, I don't see the reason why there should not be a warning if 
they could not be found while using -in1new. The altered script is 
attached for the case you like the idea and want to have a look at it.

Best regards

Björn Hülsen
Faradayweg 4-6
14195 Berlin

phone:  +49 30 8413-4863
email:  huelsen at fhi-berlin.mpg.de
www:    www.fhi-berlin.mpg.de

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