[Wien] PLEASE HELP - PROBLEMS WITH c-AXIS FOR GRAPHENE

[Rocquefelte]

Could you give me more details about your calculation ? More 
specifically, did you check the MATRIX SIZE in the scf file in the three 
calculations. It should increase dramatically when the c parameter is 
increased to 25 angstroms. Then one explanation could be that when the c 
parameter is a little bit increased (5 angstrom) the MATRIX SIZE is not 
too big in comparison to the initial calculation. However, when you use 
25 angstrom the MATRIX SIZE needed to have an accurate calculation is 
too big compare to the parameters used in the Wien2k calculation. In 
fact, I do not really know if the problem is here because I need more 
information about your calculations (Did the lapw1 and lapw2 (during the 
scf cycle) works correctly when c parameter is 25 angstrom ?). However, 
I can simply say that the increase of the c parameter will induce an 
increase of the size of the interstitial region, and then an increase of 
the number of plane waves needed to describe this region (i.e. the 
matrix size will increase).
Hope that this mail will help you.

With my best Regards

Xavier Rocquefelte



a s a écrit :
> Hello ML Folks
>
> I am running wien2k_06.4 on a PC (Intel Pentium D) with an Ubuntu 6.06 
> operating system (Ubuntu is an open source operating system built 
> around the Linux kernel).
>
> I am using a graphite .struct file to calculate the ELNES of graphene, 
> by increasing the c-axis spacing in the graphite .struct file.  
> 'initialise calc' and 'run_SCF' work perfectly.  However, I have 
> problems whenever I increase the c-axis spacing beyond a certain 
> threshold (15 Angstoms):
>
> 1. Suppose the c-axis spacing is set to 25 Angstroms.  When I run the 
> 'DOS' task, in the 'x lapw2 -qtl' step the error message "forrtl: 
> severe (174): SIGSEGV, segmentation fault occurred" is flagged.  The 
> DOS, and later the ELNES, are then not able to be calculated.
>
> 2.  Suppose I use exactly the same .struct file as for 1. above, but 
> modify solely the c-axis spacing in the .struct file to 5 Angstroms 
> (and change NOTHING else).  Everything works perfectly.  The DOS, and 
> later the ELNES, are then able to be calculated.
>
> What am I doing wrong?  Clearly, it cannot be anything to do with the 
> .struct file, since as detailed in 2. above, for c=5 Angstroms, 
> everything works perfectly.
>
> Any advice greatly appreciated.
>
> Kindest regards
>
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