[Pw_forum] Problem with pseudopotential

[W2AGZ]

Just a wild suggestion...try the PP (attached) I constructed to better model
the valence of Cu in HTSC layered copper oxide peroskites...and also change
the orbital configuration of Cu in tabd.f90 to occ_loc = 9.d0.

Like I said...a wild suggestion.  -Paul

-----Original Message-----
From: pw_forum-bounces at pwscf.org [mailto:pw_forum-bounces at pwscf.org] On
Behalf Of Nicola Marzari
Sent: Wednesday, March 30, 2011 2:29 PM
To: PWSCF Forum
Subject: Re: [Pw_forum] Problem with pseudopotential



Dear Izaak,


it seems that in Cu.pbe-d-rrkjus.UPF the average electrostatic potential
inside the slab (i.e. the average over one layer of the planar average)
would be higher than the vacuum level, so on electrostatic considerations a
test charge would want to run away. So, I'm very baffled. Any one else has
some suggestion? The two input files do look identical.

The fermi energy that you print is the one given by the slab calculation
(not really a good choice, unless you have a thick slab) or is given by
calculating in bulk cu the position of the fermi energy with respect to the
layer-average of the planar avarage, and then using that info in the slab
calculation to position the fermi energy of the bulk, and obtain the work
function?

Last - a 14% is the last of the worries - LDA and GGA seem to be all over
the place (have a look at the paper I had cited).

				nicola



On 3/30/11 4:53 PM, Izaak Williamson wrote:
> First of all, thank you so much for your replies.
>
> One more question: in the pbedrrkjus plot, there are maxima at the 
> location of each atomic layer whereas the pbevanak plot has minima. 
> What would cause this? Is it a problem?
>
>
> Both the calculations were done using exactly the same parameters but 
> different pseudopotentials. I get the following values for workfunctions.
> Cu.pbe-d-rrkjus.UPF ---> 3.956405463 eV Cu.pbe-n-van_ak.UPF ---> 
> 4.042282570 eV Experimental value ---> 4.59 eV
>
> I know that DFT-GGA calculations can underestimate the workfunctions 
> of metal surfaces, but are these acceptable values (almost a 14% error)?
>
> Thank you again for all your help.
>
>
> --
> Izaak Williamson
> Research Assistant
> Physics Department
> Boise State University


--
----------------------------------------------------------------------
Prof Nicola Marzari    Department of Materials    University of Oxford
Chair of Materials Modelling  Director, Materials Modelling Laboratory
nicola.marzari at materials.ox.ac.uk     http://mml.materials.ox.ac.uk/NM
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