[Wien] A question about RMT and AIM

[Dr. Grigori V. Vajenine]

Dear All,

A quick question on discontinuities in the calculated electron density: 
I see that in my cases and I tried to get rid of these by switching to 
LAPW as mentioned below. For that I changed the NAPWL switch in case.in1 
from 1 to 0 for all orbitals, but I still get the steps in the computed 
electron density at the RMTs (the el. dens. is higher outside of the 
spheres). What could be the reason? What did I miss?

Thanks in advance,
Grigori Vajenine
MPI-FKF
Stuttgart

A

Laurence Marks wrote:
> Aim is a hard calculation to get right because there is not currently
> any really good algorithm for finding the BCP and surface, and it is
> done by a brute force search method. What can certainly create
> problems are:
>
> 1) The discontinuities at the RMT's. You need to use very high clm's
> (in case.in2) to reduce this; for a small calculation like you have
> you may want to use an lapw basis set (rather than APW+lo) since this
> has no discontinuity. (I have a small utility to calculate the
> discontinuities.)
>
> 2) Insufficient sampling. At the end of case.outputaim there are some
> error guesstimates which are approximately correct (within a factor of
> 2). If these are large you need to increase the sampling in
> case.inaim.
>
> 3) Using too large an initial R and/or too large steps.
>
> In general, calculations with smaller RMT's should be more reliable
> albeit slower.
>
> On 11/27/06, G.C.ZHOU <gc_zhou1982 at 163.com> wrote:
>   
>>
>>  Dear Professor and users:
>>  I am doing the AIM calculation of ZnO, it has three
>> structure:wurtzite,zinc-blende and rocksalt.
>>  when I do the calculation of BCP,the other setting are all same,I find RMT
>> affect the result very greatly.
>>
>> the structure is wurtzite,
>>    and set R(Zn)=1.75, R(O)=1.85, the Laplace of BCP is 5.003;
>>    when set R(Zn)=1.85, R(O)=1.90, the Laplace of BCP is 0.580,and the
>> position of BCP is not correct.
>>
>> the structure is zinc-blende,
>>   and set R(Zn)=1.75, R(O)=1.85, the Laplace of BCP is 4.993;
>>   when set R(Zn)=1.85, R(O)=1.90, I can't find the BCP.
>>
>> the structure is rocksalt,
>>   and set R(Zn)=1.75, R(O)=1.85, the Laplace of BCP is 4.511;
>>   when set R(Zn)=1.94, R(O)=2.10, the Laplace of BCP is 3.256;
>>
>> I am puzzled with this results, but the two results of evety structure are
>> too different with only the RMT is changing. And the Laplace of rocksalt's
>> BCP tells that, in the rocksalt structure, the covanlent of Zn-O bond turns
>> more then wurtzite, it's contrary with our earlier cognition, which is the
>> bonding became more ionic in this structure.
>> even worse, when I reduce the RMT, the laplace will turns smaller yet.
>>
>> I set RKmax=9.0, LM=10, and set Ecut=-6.5Ry, there is no electron leak out.
>> and use x lapw -c to do the program.
>>
>> Can tell me why the BCP change so much in different RMT, and which
>> result should I take as the right one.
>>
>>  Any advices is welcome!
>>
>> Thanks.
>>
>>  ________________________________
>>
>> G.C.ZHOU
>> 2006-11-27
>> _______________________________________________
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>> Wien at zeus.theochem.tuwien.ac.at
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>>
>>
>>
>>     
>
>
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