[Pw_forum] Baldereschi and MP point.

[Jiayu Dai]

Thanks Stefano and Nicola. Your anwsers are so professional and very helpful. As
your comments, i guess Gamma point used in the large disordered materials and
liquids can improve the calculational efficiency twice as fast. And for symmetric
crystal, Baldereschi point works better. Am i right? And i did not find the
Baldereschi point in PWscf, so it is not implemented here?

Thanks.

In your mail:
>From: Stefano de Gironcoli <degironc at sissa.it>
>Reply-To: 
>To: Jiayu Dai <daijiayu at nudt.edu.cn>, PWSCF Forum <pw_forum at pwscf.org>
>Subject: Re: [Pw_forum] Baldereschi and MP point.
>Date:Wed, 17 Mar 2010 16:19:58 +0100
>
>Dear Jiayu Dai
>
>the Baldereschi point and MP points are efficient choice because they 
>exploit the SYMMETRY properties of the system in order to sample the BZ 
>on a hopefully small set of points.
>In liquid and disordered materials there is no symmetry and therefore 
>there is no symmetry-related k-point reduction and any regular grid of 
>points should be equally efficient.
>On the other hand for large systems the BZ shrinks and the refolded 
>bands in the mini-BZ are almost flat which means that any single point 
>in the BZ should do the work.
>In this situation Gamma is convenient because  wfc (in absence of 
>spin-orbit) can be chosen as real in real space which implies that wfc 
>Fourier components of G and -G are related  by complex conjugation and 
>you can use half the memory storage and cut by two the number of operations.
>
>best,
>  stefano
>
>Jiayu Dai wrote:
>> Dear users, 
>>
>> I have a question about the sample points in the Brillouin zone. We usaually
use
>> the MP point in our calculations, and it works well and fast in cubic crystal.
>> However, for disordered materials or liquids, we usually use Gamma point only,
>> such as point in CPMD. My question is how do we know the Gamma point is better
>> than the Baldereschi mean value point, or on the contrary£¿Which one gives
faster
>> convergence?
>>
>> Thanks a lot.
>>
>> Jiayu
>>
>>
>>
>>
>> ------------------------------
>> -------------------------------------------
>> Jiayu Dai
>> Department of Physics
>> National University of Defense Technology, 
>> Changsha, 410073, P R China
>> -----------------------------------------
>>   
>> ------------------------------------------------------------------------
>>
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>
>
> 




------------------------------
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Jiayu Dai
Department of Physics
National University of Defense Technology, 
Changsha, 410073, P R China
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