[Wien] resolution dependent F(HKL)s from lapw3
Laurence Marks
L-marks at northwestern.edu
Wed Aug 22 18:55:43 CEST 2012
Peter can/will probably make some comments. From what I can remember,
lapw3 is an old, not completely optimized code. If you dig through it
(which you may have to do for what you appear to want) you will find
it does a convolution to correct the PW's so they are zero within the
spheres, and a numerical transform for the density within the spheres.
Both are probably going to depend upon the sampling (largest HKL used)
and for certain you will need a large RKMAX and GMAX as otherwise the
PW's will be truncated (inspect case.clmsum -- are the high angle
values you want there?)
The main use of lapw3 in the past has been for the lower-angle values
that are affected by bonding and these are OK although there are some
issues (dig into the literature on charge density comparisons)
particularly at high angles which have to do with how the core states
are calculated. Search for "charge density" on the Wien2k publications
page.
On Wed, Aug 22, 2012 at 11:32 AM, Georg Eickerling
<georg.eickerling at physik.uni-augsburg.de> wrote:
> Dear WIEN users,
>
> I noticed a strange behavior of lapw3 which I do not understand:
>
> Take for example a simple diamond case and calculate structure
> factors from clmsum, lets say up to sin theta/lambda = 1.0:
>
> 0 0 0 0.0000000 12.0000251726
> -1 -1 -1 0.2427814 -4.6536716863
> 0 0 -2 0.2803398 0.0000000000
> 0 -2 -2 0.3964603 -3.9459734623
> -1 -1 -3 0.4648909 -2.3988162763
> -2 -2 -2 0.4855627 0.2266152403
> 0 0 -4 0.5606796 -3.1297582248
> -1 -3 -3 0.6109864 2.2069300710
> 0 -2 -4 0.6268588 0.0000000000
> -2 -2 -4 0.6866894 2.8777607788
> -3 -3 -3 0.7283441 1.9393120414
> -1 -1 -5 0.7283441 1.9663566686
> 0 -4 -4 0.7929206 2.6458269883
> -1 -3 -5 0.8292562 1.8056937118
> -2 -4 -4 0.8410193 -0.0171687161
> 0 0 -6 0.8410193 0.0000000000
> 0 -2 -6 0.8865122 2.4363270068
> -3 -3 -5 0.9191554 -1.6841664183
> -2 -2 -6 0.9297818 -0.0087306004
> -4 -4 -4 0.9711255 -2.2589221048
>
> Repeating this calculation with sin theta/lambda = 1.1 and a diff
> with the old hkl will just show the additional reflections as expected:
>
> diff hkl.10 hkl.11
> 20a21,26
>> -1 -5 -5 1.0010132 1.6970975057
>> -1 -1 -7 1.0010132 1.5391902602
>> 0 -4 -6 1.0107794 0.0000000000
>> -2 -4 -6 1.0489354 -2.0944311378
>> -3 -5 -5 1.0766653 -1.4379800081
>> -1 -3 -7 1.0766653 -1.4425910379
>
> Now again repeat the calculation with sin theta/lambda = 1.2:
>
> diff hkl.11 hkl.12
> 25,26c25,32
> < -3 -5 -5 1.0766653 -1.4379800081
> < -1 -3 -7 1.0766653 -1.4425910379
> ---
>> -3 -5 -5 1.0766653 -1.4106390375
>> -1 -3 -7 1.0766653 -1.4699320085
>> 0 0 -8 1.1213591 1.9443586030
>> -3 -3 -7 1.1473400 1.3618747163
>> -4 -4 -6 1.1558705 0.0030399053
>> 0 -2 -8 1.1558705 0.0000000000
>> 0 -6 -6 1.1893809 1.7411783356
>> -2 -2 -8 1.1893809 -1.8133181764
>
> What happens here? Why are reflections which were exactly the same
> before suddenly different? Why I worry about this is, that if you go
> on increasing the resolution, the differences become more severe
> than in the example above, i.e. sin theta/lambda = 1.3:
>
> diff hkl.12 hkl.13
> 21,22c21,22
> < -1 -5 -5 1.0010132 1.6970975057
> < -1 -1 -7 1.0010132 1.5391902602
> ---
>> -1 -5 -5 1.0010132 -1.5542465484
>> -1 -1 -7 1.0010132 1.5480881986
>
> On the other hand, the differences "converge" for a given reflection
> but more and more become "affected", i.e. sin theta/lambda = 1.8
> vs. 1.2:
>
>
> diff hkl.12 hkl.18
> 21,22c21,22
> < -1 -5 -5 1.0010132 1.6970975057
> < -1 -1 -7 1.0010132 1.5391902602
> ---
>> -1 -5 -5 1.0010132 -1.5542465484
>> -1 -1 -7 1.0010132 1.5480881986
> 25,26c25,26
> < -3 -5 -5 1.0766653 -1.4106390375
> < -1 -3 -7 1.0766653 -1.4699320085
> ---
>> -3 -5 -5 1.0766653 -1.4379800081
>> -1 -3 -7 1.0766653 -1.4425910379
> 28c28
> < -3 -3 -7 1.1473400 1.3618747163
> ---
>> -3 -3 -7 1.1473400 -1.3370357923
> 31c31
> < 0 -6 -6 1.1893809 1.7411783356
> ---
>> 0 -6 -6 1.1893809 -1.8136982305
>
>
> Looking at the result of a refinement of a structural model against
> the different HKLs, the "high resolution version" seems to be
> "wrong" compared to the low-res one.
>
> Thank you very much in advance for any comments on this.
>
> regards
>
> Georg Eickerling
>
>
> --
> ============================
> Dr. Georg Eickerling
> Universitaet Augsburg
> Institut fuer Physik
> Lehrstuhl fuer Chemische Physik und Materialwissenschaften
> Universitaetsstr. 1
> 86159 Augsburg
>
> E-Mail: georg.eickerling at physik.uni-augsburg.de
> Phone: +49-821-598-3362
> FAX: +49-821-598-3227
> WWW: http://www.physik.uni-augsburg.de/cpm/
> =====================================================
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--
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu 1-847-491-3996
"Research is to see what everybody else has seen, and to think what
nobody else has thought"
Albert Szent-Gyorgi
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