[Pw_forum] Question about Work Function calculation

[Ali KACHMAR]

Hi,

Have a look at this paper and see how they did the 
convergence of the work function wrt the slab thickness, vacuumm, 
K-mesh.......

http://prb.aps.org/abstract/PRB/v80/i23/e235407

You will find interesting information about the work function on the pwscf archive. 

Please
 don't forget that the input values in the workfunction example are not 
converged and you need to converge your own input values for the system 
are you working on.

Best,
Ali

Date: Fri, 1 Feb 2013 11:03:40 -0800
From: nmn_nariman at yahoo.com
To: pw_forum at pwscf.org
Subject: [Pw_forum] Question about Work Function calculation

Dear PWSCF users/developers,
I have started to learn how to calculate work function for modified Ge-surfaces with organic molecules. The WF_example was very helpful but still there is something that I dont understand:
1) How slab potential is calculated in the example and why macroscopic average for the energy E = "17.8087" Ry is taken? ( I thought it's the middle point but its not)2) Matching macroscopic/planar averages at the borders in the case of modified surfaces needs lots of vacuum. Is the vacuum length the only effective parameter here? How accurate matching should be?(In my case sometimes for same chains but different lengths I need to give longer vacuum for shorter chain compare to longer one to achieve the matching!!! is it logical? )
I have read all the posts for work function but didn't get my answer. Any idea is highly appreciated,
Regards,
DanielElectronic Engineering Department, UCC, Ireland 
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