[Pw_forum] How to get vacuum level

[Stefano Baroni]

Work function = (average potential in the vacuum) - (Fermi Energy)
So you had the solution already, the missing (and not very surprising)  
step is the identification of the vacuum level with the average of the  
potential "out in the vacuum" (as discussed many, many times in this  
forum as well as many, many times in the literature)

SB

On Nov 14, 2008, at 3:36 AM, oulihui666 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 points 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  
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
http://www.sissa.it/~baroni / [+39] 040 3787 406 (tel) -528 (fax) /  
stefanobaroni (skype)

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