[Pw_forum] Doubt in workfunction example for Al100
Bipul Rakshit
bipulrr at gmail.com
Tue Apr 7 09:18:54 CEST 2015
Dear users,
how to choose the following values, for the dipole correction?
emaxpos=0.6,
eopreg=0.06,
eamp=0.00,
I am doing a calculation of 6layers of Au and 8 double layers of ZnO with
20 Ang of vaccum. I want to calculate the workfunction of it. I saw in the
example (dipole_example) in PP/example directory, that changing these
values a little bit changes the result quite a bit. So kindly suggest me
how to decide these values. Though I read in the INPUT_PW.txt about there
description, but unable to understand.
regards
On Mon, Mar 30, 2015 at 4:27 PM, Giovanni Cantele <
giovanni.cantele at spin.cnr.it> wrote:
> Provided that you have a sufficient number of layers to guarantee in both
> sides a “bulk-like” region, you can choose the innermost layers.
>
> But, because you have an interface, what is the quantity are you
> interested in? The interface barrier (in your case the Schottky barrier,
> because you have a metal-semiconductor
> junction) or the work function? Consider that, in the latter case, because
> the two sides of the slab are different:
> i) the vacuum level is different at the two sides, so you just choose the
> interplanar distance of the material you are interested in (either ZnO or
> Au)
> ii) because the vacuum level is different at the two sides, you must
> consider to add a correction for a “spurious” dipole introduced by boundary
> conditions, using tefield=.true.
> dipfield=.true., and the related variables (see
> PW/DOC/INPUT_PW.txt for explanation) edit, eamp=0.D0, eopreg and examples
>
> In the case you are instead interested in the interface barrier, you
> easily figure out that by choosing, as the window for the macroscopic
> average either the ZnO or the Au interplanar distance you get rid of
> microscopic oscillations only on one side. In this case, you can compute
> the averages with both windows, and plot them on the same plot. If needed,
> you might want to have a look at Fig. 6 of N.R. D’amico, et al, J. Phys.:
> Condens. Matter 27 (2015) 015006
>
> Hope this helps,
>
> Giovanni
>
> PS Warning: the ZnO orientation you are studying is polar, so the
> macroscopic average does not give you a constant value of the potential in
> the innermost part of the ZnO slab,
> but a linearly varying one. There are examples in the literature on how
> the handle the electrostatic potential in polar slabs, see references in
> the above mentioned paper.
>
>
>
> On 30 Mar 2015, at 11:47, Bipul Rakshit <bipulrr at gmail.com> wrote:
>
> Really thanks for your suggestion Giovanni,
> I just have few more doubts that if i want to find the work function of
> Au-ZnO Slab. I have created Au(111) and ZnO(0001) Slab. So it has an
> interface of Zn-Au and a vacuum of 10 Angstrom. I took 6 layers of Au and 4
> double layers of ZnO. Then how to proceed.
> Means
> 1) Which two consecutive atomic planes I have to choose Au-Au, Au-Zn or
> the Zn-O planes. for the microscopic average calculation?
>
> 2) Also in-order to choose the inner part of the slab, so that part is
> inside the Au-Slab or the ZnO Slab?
>
> regards
>
>
> On Wed, Mar 18, 2015 at 5:02 PM, Giovanni Cantele <
> giovanni.cantele at spin.cnr.it> wrote:
>
>> The average electrostatic potential you are calculating/plotting does
>> show microscopic oscillations, revealing the atomic planes
>> (plot the 2d column of reference/Al100.avg.out as a function of the 1st
>> one).
>>
>> The calculation of the work function requires a “constant” energy level
>> to compare the bulk and the slab calculation. For this purpose,
>> you run a macroscopic average of the x-y averaged electrostatic
>> potential. The window you choose for the macroscopic average
>> is just the distance between two consecutive atomic planes (in a.u.).
>> Because the input positions are in alat units, you get
>>
>> (2.8284271247461898 - 2.1213203435596428) * 5.4235090117 = 3.835
>>
>> In this way, microscopic oscillations with period 3.835 are averaged and
>> a constant level (in the inner region of the slab) is obtained.
>>
>> Concerning 17.8087, in order to get this constant value, you can choose
>> any position in the inner part of the slab where the
>> macroscopic average does not show significant variations.
>>
>> Giovanni
>>
>>
>> On 18 Mar 2015, at 10:49, Bipul Rakshit <bipulrr at gmail.com> wrote:
>>
>> In espresso, there is an example to find the workfunction of Al. In the
>> run_example, the input for the the macroscopic average is the following
>> cat > Al100.avg.in <http://al100.avg.in/> <<EOF
>> 1
>> Al100.pot
>> 1.D0
>> 1440
>> 3
>> 3.835000000
>> EOF
>>
>> In this file the quantity "3.835" i saw in average.f90 as "awin !
>> the size of the window for macroscopic averages"
>>
>> So my doubt is how we can choose this no. Can we get the information from
>> another file prerun file, like Al100.pot, or something else.
>>
>> Also in run_example there is another quantity vSlab
>>
>> vSlab=`grep "17.8087" Al100.avg.out | cut -d \ -f 10`
>>
>> So how the value correspond to "17.8087" is assign as vSlab?
>>
>> Kindly help me in this matter.
>>
>> regards
>> --
>> Dr. Bipul Rakshit
>> Research Associate,
>> Institute of Physics (IOP),
>> Bhubaneswar- 751 005
>> Orissa
>> India
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://pwscf.org/mailman/listinfo/pw_forum
>>
>>
>> --
>>
>> Giovanni Cantele, PhD
>> CNR-SPIN
>> c/o Dipartimento di Fisica
>> Universita' di Napoli "Federico II"
>> Complesso Universitario M. S. Angelo - Ed. 6
>> Via Cintia, I-80126, Napoli, Italy
>> e-mail: giovanni.cantele at spin.cnr.it
>> Phone: +39 081 676910
>> Skype contact: giocan74
>>
>> ResearcherID: http://www.researcherid.com/rid/A-1951-2009
>> Web page: http://people.na.infn.it/~cantele
>>
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://pwscf.org/mailman/listinfo/pw_forum
>>
>
>
>
> --
> Dr. Bipul Rakshit
> Research Associate,
> Institute of Physics (IOP),
> Bhubaneswar- 751 005
> Orissa
> India
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
>
> --
>
> Giovanni Cantele, PhD
> CNR-SPIN
> c/o Dipartimento di Fisica
> Universita' di Napoli "Federico II"
> Complesso Universitario M. S. Angelo - Ed. 6
> Via Cintia, I-80126, Napoli, Italy
> e-mail: giovanni.cantele at spin.cnr.it
> Phone: +39 081 676910
> Skype contact: giocan74
>
> ResearcherID: http://www.researcherid.com/rid/A-1951-2009
> Web page: http://people.na.infn.it/~cantele
>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
--
Dr. Bipul Rakshit
Research Associate,
Institute of Physics (IOP),
Bhubaneswar- 751 005
Orissa
India
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