[Pw_forum] About maximally localized wannier function

[Silviu Zilberman]

Dear Nicola,

Thank you for your detailed explanation. Following on your last point, 
suppose you do the best k-point sampling with PW, to obtain the total 
charge density. One could impose this charge density in the CP 
calculation, at every step, to get MLWF at the gamma-point that are 
consistent with this charge density. Wouldn't it implicitly be 
equivalent to the MLWF obtained in the full k-points optimization?

Thanks, Silviu.

Nicola Marzari wrote:

>
>
> Dear Silviu,
>
> this is an interesting suggestion. The good thing about the
> Gamma-sampling CP code algorithm is that it will always lead to
> the true minimum of the localization functional, as long as a
> cubic/tetragonal/orthorombic cells are used (i.e. derivatives are
> calculated with 3 orthogonal G vectors). Depending on your application,
> this could be very important or irrelevant - the more the system is 
> large and disordered, the more it becomes useful/essential.
> Another advantage is that the CP/Wannier subroutines work with ultrasoft
> pseudopotentials, although this capability is forthcoming in 
> wannier-transport.org and wannier.org .
>
> The regular k-point wannier codes use instead trial projection orbitals
> (very straightforward  ones - usually one specifies the center of a
> gaussian, and the l,m of a spherical harmonics) to start the 
> minimization already in the right basin of attraction. This
> approach works again very well in most cases - to the point that some 
> groups just use these projections, without localization, to get
> localized WFs (I think, e.g., Pickett's group).
>
> As a last note - if you use CP, your sampling can be "poor" if you have
> a smallish unit cell. On the other hand, if you use PWSCF to feed CP,
> you can make your charge density as good as you want it, sampling-wise.
> Then, the only finite-size errors remaining will be on the calculation
> of the MLWFs themselves, that, using CP, will only combine states
> obtained at Gamma, instead of using all the Brillouin zone.
>
>                 nicola
>
>
> Silviu Zilberman wrote:
>
>> Dear Xianghjun,
>>
>> MLWF are implemented in the CP code. I believe that the latest cvs 
>> version has compatible restart files, which means you could use any 
>> PWSCF calculation result as an input to a CP Wannier calculation. 
>> This compatibility has only been introduced recently, and it may 
>> still be unstable. You could also take the geometry from your PW 
>> calculation and start a CP calculation from scratch and minimize the 
>> wavefunction using Wannier dynamics. Look at the INPUT_CP file for 
>> more details, as well as example #23.
>>
>> Silviu.
>>
>> xianghjun wrote:
>>
>>> Dear all,
>>>  I am trying to get MLWF for some systems and want to know if MLWF 
>>> has been implemented in PWSCF.
>>> Thanks in advance.
>>>
>>> Best regards,
>>> xianghjun
>>>
>>> =============================================================
>>> H. J. Xiang
>>> Ph.D. Candidate,
>>> Hefei National Laboratory For Physical Sciences at Microscale,
>>> University of Science and Technology of China,
>>> Hefei, Anhui, 230026,
>>> People's Republic of China
>>> Tel.: 86-551-3606428
>>> Fax.: 86-551-3602969
>>> E-mail: xhongjun at mail.ustc.edu.cn
>>> =============================================================
>>>
>>> _______________________________________________
>>> Pw_forum mailing list
>>> Pw_forum at pwscf.org
>>> http://www.democritos.it/mailman/listinfo/pw_forum
>>
>>
>>
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
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>
>


-- 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Zilberman Silviu
 
213 Frick Laboratory, Department of Chemistry 
Princeton University
Princeton, NJ 08544
 
phone: 609-258-1834
fax:   609-258-6746
silviu at Princeton.EDU
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