[Pw_forum] Oscillations in macroscopic average of VH+Vbare

Gabriele Sclauzero sclauzer at sissa.it
Mon May 2 09:30:09 CEST 2011

You need to consider a slab with equally spaced atomic planes (at least in the inner part; you may allow to relax the outern planes, I think) and to choose an appropriate width for the window of the macroscopic average. If you do this correctly, you should not see these oscillations in the slab interior.



Il giorno 29/apr/2011, alle ore 23.33, Izaak Williamson ha scritto:

> Dear all,
> I am trying to calculate the work function for Cu(100) surface with and without bulk reference. The equations used are as follows:
> work function w/o bulkref  -->  wf1 = Vvac - EF,slab 
> work function with bulkref  -->  wf2 = Vvac - Vslab,int + Vbulk,macro - EF,bulk
> The problem is that the macroscopic average of VH+Vbare for the slab is oscillating as a function of z (see 05.png). I do not understand why the macroscopic average is oscillating. We want to see the convergence of the work function with the number of atomic layers in the slab. Due to the oscillation in macroscopic average,  the work function dramatically changes when we go from 5 to 6 layers (4.86641 eV to 3.62728 eV, respectively). This makes it hard to see the convergence of wf with number of layers.
> Would it be correct to use the average of the macroscopic average of the peaks and troughs in calculating wf2? Even if we calculate the average of upper oscillations (05.png), I don't know what to do with the trough that comes up just before the vacuum region?
> Thank you for any help.
> -- 
> Izaak Williamson
> Research Assistant
> Physics Department
> Boise State University
> <05.png><Al100.wf.png>_______________________________________________
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne

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