[Pw_forum] How to get vacuum level

[lan haiping]

in fact , this question has been asked for many times in the forum.  Just do
a refined search with 'workfunction ' or '
vacuum level ' keywords in google or other engines will
help you a lot.    And there is also a example about how
to do workfunction's calculation  supplied with QE, which
you can find in $QE/examples/WorkFct_example.

how to define vacuum level ?  a simple or handwaving picture is to do plane
average of electrostatic potential
perpendicular to vacuum layer.  If your vacuum layer is
thick enough, you should find a constant value in the vacuum   layer region.
This value , you then can refer to
so-called vacuum level.


On Fri, Nov 14, 2008 at 10:36 AM, oulihui666 <oulihui666 at 126.com> wrote:

> Dear pwscf users,
> I want to calculate work function, I have got the fermi level, so I must
> get the vacuum level.
>  *work = (vacuum level) - (fermi level)*
>
> My input file displayed as follows:
>
> (1)scf calculation:
>
> &control
>     calculation='scf'
>     restart_mode='from_scratch',
>     prefix='Al',
>     pseudo_dir = './',
>     outdir='./'
>  /
>  &system
>     ibrav=  0,  nat=11, ntyp= 1,
>     ecutwfc =16,
>     occupations='smearing', smearing='methfessel-paxton', degauss=0.01
>  /
>  &electrons
>     conv_thr =  1.0d-8
>     mixing_beta = 0.7
>  /
> CELL_PARAMETERS cubic
> 5.41176    0    0
> 0    5.41176    0
> 0    0        60.9909
> ATOMIC_SPECIES
> Al 13.867     Al.vbc.UPF
> ATOMIC_POSITIONS {angstrom}
> Al    0    0    0
> Al    1.43189    1.43189    2.025
> Al    0    0    4.05
> Al    1.43189    1.43189    6.075
> Al    0    0    8.1
> Al    1.43189    1.43189    10.125
> Al    0    0    12.15
> Al    1.43189    1.43189    14.175
> Al    0    0    16.2
> Al    1.43189    143189    18.225
> Al    0    0    20.25
> K_POINTS {automatic}
>   8  8 1  0 0 0
>
> (2)Electrostatic potential calculation:
>
>  &inputpp
>     prefix  = 'Al'
>     outdir = './'
>     filplot = 'Al.pot'
>     plot_num= 11
>  /
>
> (3)macroscopic averages calculation: average.x.
>
> 1
> Al.pot
> 1.D0
> 5000
> 3
> 2.95
>
> Finally, I get a output file, column 1: coordinate u, *defined over a mesh
> of npt=5000 point*s along the direction idir=3, column 2: *averaged
> quantity* V,
>
> column 3: *macroscopically averaged quantity V*,  I should how to get the
> vacuum level? any suggestion will be appreciated.
>
>
>
> Thank you
>
> Lihui Ou
>
> --
>  ======================================
> Lihui Ou
> PH.D Candidate in Electrochemistry
> College of Chemistry and Molecular Science
> Wuhan University,*430072*,Hubei Province,China
> *E-mail:oulihui666 at 126.com*
> ======================================
>
>
> ------------------------------
> 网易邮箱10周年,技术见证辉煌 <http://www.yeah.net>
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>


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