[Wien] "Best" RMT for a given total matrix size

[Peter Blaha]

I guess your procedure is correct.
The ration of RMTs is elementspecific.
In principle we have tried to incorporate such knowledge in    setrmt   
script. Eg. Ti (as 3d element) will get a 10% larger RMT than O, which is 
quite close to your findings. I would NOT expect, that small variations of 
RMT will make a big difference.

However, I'm not sure if setrmt is clever enough for all cases and there 
might be combinations of elements where setrmt does not give an optimum 
yet.

> I often run into problems where it is not possible to run as large an RKMAX as
> I would like, so the issue is how to choose the "best" RMT for a given case. I
> would like to suggest an idea, and others can either give alternative
> suggestions and/or point out my error.
> 
> The concept is this. For a fixed matrix size (by adjusting RKMAX
> appropriately), run a series of small calculations (e.g. a simple bulk
> material) varying the RMT's to find the lowest energy. For instance, with a
> binary AB run with RMT_B=constant-RMT_A with some steps around the values
> given by setrmt to find the lowest energy. The results appear to be
> reasonable, for instance with TiO2 this gives
>        RMT_Ti = RMT_O + 0.18
> 
> The rationalization is that in the spirit of the variational principle, the
> best RMT combination for a given size should give the lowest energy......
> 
> Note: if you have an old email address for me, please note that "nwu" has
> been changed to "northwestern".
> -----------------------------------------------
> Laurence Marks
> Department of Materials Science and Engineering
> MSE Rm 2036 Cook Hall
> 2225 N Campus Drive
> Northwestern University
> Evanston, IL 60208, USA
> Tel: (847) 491-3996 Fax: (847) 491-7820
> email: L-marks at northwestern dot edu
> http://www.numis.northwestern.edu
> -----------------------------------------------
> 
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                                      P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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