[Pw_forum] Baldereschi and MP point.

[Stefano de Gironcoli]

Baldereschi's point or any set of points can be provided using  input 
formats "tpiba" or "cystal" that reads the number of k-points in the 
list and then a line for each point with coordinate (in unit of 2PI/a 
{tpiba} or as fraction of the reciprocal lattice vectors {crystal}) and 
its weight.

stefano

Jiayu Dai wrote:
> 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
>>> -----------------------------------------
>>>   
>>> ------------------------------------------------------------------------
>>>
>>> _______________________________________________
>>> Pw_forum mailing list
>>> Pw_forum at pwscf.org
>>> http://www.democritos.it/mailman/listinfo/pw_forum
>>>   
>>>       
>>
>>     
>
>
>
>
> ------------------------------
> -------------------------------------------
> Jiayu Dai
> Department of Physics
> National University of Defense Technology, 
> Changsha, 410073, P R China
> -----------------------------------------
>   
> ------------------------------------------------------------------------
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>