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[lan haiping <lanhaiping@gmail.com>]

Hi, Aaron :

There are quite a lot works on NFE of  nano-carbon systems, if you pay attention to the topics of n-type doping. You may have  a look through  an interesting work by Vincent Crespi :PRL 96 196803.


Cheers,
Hai-Ping

On Thu, Aug 20, 2009 at 2:07 AM, Aaron Zhou <fishzhou@gmail.com> wrote:

Dear Nicola and Matthieu,

Thank you very much!

Is there any literature talking about FEL states? or FEL review paper,
because there are so many papers there that I don't know where to
start from.

Thanks again!!

Aaron

On Wed, Aug 19, 2009 at 6:30 AM, matthieu
verstraete<matthieu.jean.verstraete@gmail.com> wrote:
> Nicola is correct, these are free electron like (FEL) states, which I
> have found as well, and also in a few published results see PHYSICAL
> REVIEW B 68, 155424 2003 fig 7 (or PRL 101, 226405 (2008) fig 1). For
> the GW correction I do not find the same sign as they do in the prb,
> but it depends delicately on how fully converged you are wrt the FEL
> states. The calculations always give perfectly reasonable BS near the
> Fermi level. The states will keep coming down and create a dense
> continuum as you increase the cell size. The lowest FEL state will
> converge, but as you add bands and vacuum the rest will densify and
> superimpose on the "normal" bandstructure of graphene. I insist they
> are physical, and constitute a kind of unbound continuum of states,
> corresponding to the interlayer graphite states.
>
> Why VASP does not have them I don't know... very strange... perhaps
> the way the states are represented based on the PAW, but that would be
> wierd. The scf algorithm is a possibility, if for some reason it
> prefers localized states and misses lower energy delocalized ones. How
> far have you pushed the vacuum? I would expect problems with, e.g.,
> siesta for delocalized states far from the atoms, but not with another
> PW/PAW code.
>
> Matthieu
>
>
>
> On Wed, Aug 19, 2009 at 10:56 AM, Nicola Marzari<marzari@mit.edu> wrote:
>>
>>
>> Dear Aaron,
>>
>>
>> very interesting. Could it be that those bands are free electron like bands
>> that live mostly in
>> the vacuum region, and are lowered in energy when they are less confined
>> (more spacing
>> between the confining graphene layers) ? Interlayer bands in graphite have
>> been discussed since
>> ~30 years ago (I believe by Posternak and Baldereschi), and 2-3 years ago in
>> relation with
>> superconductivity in intercalated graphite (Csanyi et al - I believe Nature
>> Materials).
>>
>> Why they do not appear in Vasp might be related to the DIIS algorithm ? I
>> believe DIIS
>> is not guaranteed to converge to the sequence of lowest eigenstates, just to
>> eigenstates. Can
>> you use a different algorithm ?
>>
>>            nicola
>>
>>
>>> On Tue, Aug 18, 2009 at 11:53 PM, Aaron Zhou<fishzhou@gmail.com> wrote:
>>>
>>>>
>>>> Dear all,
>>>>
>>>> I have a question when calculating graphene band structure. I leave a
>>>> 10 angstrom vacuum in Z-direction. But I saw many extra bands which
>>>> don't exist when doing the same thing in VASP. So I did a series of
>>>> calculation only changing the vacuum size, from 3A to 15A. I saw some
>>>> excited bands are pushed down from higher energy. Even 8 angstrom
>>>> vacuum and 10 angstrom vacuum will make big difference. That is quite
>>>> unexpected! I think the vacuum is already big enough to see the
>>>> convergence in band structure.
>>>>
>>>> Could someone tell me why those conduction bands are pushed down when
>>>> changing the vacuum size (acell(3) in input file)?
>>>>
>>
>>
>> --
>> ---------------------------------------------------------------------
>> Prof Nicola Marzari   Department of Materials Science and Engineering
>> 13-5066   MIT   77 Massachusetts Avenue   Cambridge MA 02139-4307 USA
>> tel 617.4522758 fax 2586534 marzari@mit.edu http://quasiamore.mit.edu
>>
>
>
>
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Dr. Matthieu Verstraete
>
> European Theoretical Spectroscopy Facility (ETSF)
> Dpto. Fisica de Materiales,
> U. del Pais Vasco,
> Centro Joxe Mari Korta, Av. de Tolosa, 72,   Phone: +34-943018393
> E-20018 Donostia-San Sebastian, Spain        Fax  : +34-943018390
>
> Mail : matthieu.jean.verstraete@gmail.com
> http://www-users.york.ac.uk/~mjv500
>
>

-- 
Hai-Ping Lan 
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping@gmail.com, hplan@pku.edu.cn