[Pw_forum] Doubt in workfunction example for Al100

[Giovanni Cantele]

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
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-- 

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

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