The ABINIT Users Mailing List ( CLOSED )

["Matteo Giantomassi" <Matteo.Giantomassi@uclouvain.be>]

> Dear Xavier and Fabien,
>
>    I do wonder  whether extrapolar method is implemented in PAW scheme for
> GW calculations ?
>

 No, it's not yet available.

> Regards,
> Hai-Ping
> On Sat, Apr 25, 2009 at 2:11 AM, Xavier Gonze
> <xavier.gonze@uclouvain.be>wrote:
>
>> Dear Manuel,
>>
>> On 15 Apr 2009, at 12:34, Manuel Pérez Jigato wrote:
>>
>>  Dear all
>>>
>>> Regarding the extrapolar method, i would like to find out
>>>
>>> - Is the approximate method to determine the best value of gwencomp
>>> based on the completeness relation and plasma frequency, implemented in
>>> abinit?
>>>
>>
>> You can monitor the effect described in the paper using abinit, but it
>> is
>> not automatic. At present,
>> some people proceed as follow :
>> - take a reasonable value of gwencomp, like 2 Hartree, and plot a few
>> (e.g.
>> three) values of the
>>  eigenenergy (or gap) as a function of nband
>> - on the basis of the curvature of this property, either increase of
>> lower
>> the value of gwencomp (e.g. 1 Ha or 3 Ha)
>> Usually one finds that these two curves constitute a bound on the
>> converged
>> value (so, somehow, an error bar).
>> This is quite convenient ...
>>
>>
>>>
>>> - According to the paper, the suggested value is 2 Hartree.
>>> I guess that when the number of bands is very high, you need to
>>> increase
>>> gwencomp?
>>>
>>
>> No, gwencomp can be left unchanged, whatever the number of bands.
>>
>>>
>>>
>>> - Is the extrapolar method always benefitial? ie, are there no
>>> requirements/conditions for a particular system to require a smaller
>>> number
>>> of bands (than the standard nband using the full continuum)?
>>>
>>
>> No, until now, we have always seen it to be beneficial, for bulk solids,
>> isolated molecules as well as nanowires.
>>
>>
>>>
>>> thanks a lot
>>>
>>>
>> Regards,
>> Xavier
>>
>>
>>  --
>>> Manuel Pérez Jigato
>>> KU Leuven
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
> --
> Hai-Ping Lan
> Department of Electronics ,
> Peking University , Bejing, 100871
> lanhaiping@gmail.com, hplan@pku.edu.cn
>