[Pw_forum] Work function issues

[Hepplestone, Steven]

Dear all,

I am having difficulties with calculating the work function of various metals 
(Au and Pt in particular) using the X.pbe-mt_fhi.UPF and X.pbe-n-nc.UPF pseudo 
potentials.  Unlike in the example in WorkFct_example in PP I am regularly 
getting a positive Fermi energy and a vacuum level which is lower than the 
average level for the potential of the atoms.  Is this a case of poor pseudo 
potential choice, a bug or user error?

Any advice would be appreciated,

Kind regards

Steven


Dr. Steven Hepplestone
Physics
University of Exeter
Stocker Road
Exeter
EX4 4QL
Ext.: +44 (0)1392 723048
Int.: 3048



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Re: [Pw_forum] Work function issues

[Ian Shuttleworth]

Hi Steven

I've just used H and Pt.pbe-mt_fhi.UPF recently and investigated work
function (amongst other things) and I didn't encounter any problems:

Controlled FCC/on-top binding of H/Pt(111) using surface stress

http://dx.doi.org/10.1016/j.apsusc.2016.03.173


With thanks


Ian

On Thu, Apr 21, 2016 at 4:57 PM, Hepplestone, Steven <
s.p.hepplest...@exeter.ac.uk> wrote:

> Dear all,
>
>
>
> I am having difficulties with calculating the work function of various
> metals (Au and Pt in particular) using the X.pbe-mt_fhi.UPF and
> X.pbe-n-nc.UPF pseudo potentials.  Unlike in the example in WorkFct_example
> in PP I am regularly getting a positive Fermi energy and a vacuum level
> which is lower than the average level for the potential of the atoms.  Is
> this a case of poor pseudo potential choice, a bug or user error?
>
>
>
> Any advice would be appreciated,
>
>
>
> Kind regards
>
>
>
> Steven
>
>
>
>
>
> Dr. Steven Hepplestone
>
> Physics
>
> University of Exeter
>
> Stocker Road
>
> Exeter
>
> EX4 4QL
>
> Ext.: +44 (0)1392 723048
>
> Int.: 3048
>
>
>
> ___
> Pw_forum mailing list
> Pw_forum@pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
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Re: [Pw_forum] Work function issues

[Hepplestone, Steven]

Thank you for the feedback, but it doesn’t explain what error I must be making.

I attach to this email an image of the local potential generated by my input 
file (after processing with a similar code to average.x).  I cannot see what 
mistake I am making with the work function calculation.

Any advice would be gladly appreciated at this stage.

Steve

From: pw_forum-boun...@pwscf.org [mailto:pw_forum-boun...@pwscf.org] On Behalf 
Of Ian Shuttleworth
Sent: 21 April 2016 18:05
To: PWSCF Forum 
Subject: Re: [Pw_forum] Work function issues

Hi Steven

I've just used H and Pt.pbe-mt_fhi.UPF recently and investigated work function 
(amongst other things) and I didn't encounter any problems:


Controlled FCC/on-top binding of H/Pt(111) using surface stress

http://dx.doi.org/10.1016/j.apsusc.2016.03.173



With thanks



Ian

On Thu, Apr 21, 2016 at 4:57 PM, Hepplestone, Steven 
mailto:s.p.hepplest...@exeter.ac.uk>> wrote:
Dear all,

I am having difficulties with calculating the work function of various metals 
(Au and Pt in particular) using the X.pbe-mt_fhi.UPF and X.pbe-n-nc.UPF pseudo 
potentials.  Unlike in the example in WorkFct_example in PP I am regularly 
getting a positive Fermi energy and a vacuum level which is lower than the 
average level for the potential of the atoms.  Is this a case of poor pseudo 
potential choice, a bug or user error?

Any advice would be appreciated,

Kind regards

Steven


Dr. Steven Hepplestone
Physics
University of Exeter
Stocker Road
Exeter
EX4 4QL
Ext.: +44 (0)1392 723048
Int.: 3048


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Re: [Pw_forum] Work function issues

[Giovanni Cantele]

Maybe it is neither a poor pseudo potential choice nor a bug or user error.

Using for example Au.pbe-mt_fhi.UPF  I get

Fermi level ~ 3.30 eV
vacuum level ~ 8.48eV

with a plot similar to what you attach in a follow-up e-mail.
That corresponds to a ~ 5.17 gold work function, not that far from literature 
results, see, e.g., PHYSICAL REVIEW B 80, 235407 2009 .

Take care of slab thickness convergence issues as well as of the fact that a 
more accurate calculation might require a bulk crystal calculation,
see details in the above reported reference.

Giovanni
> On 21 Apr 2016, at 17:57, Hepplestone, Steven  
> wrote:
> 
> Dear all,
>  
> I am having difficulties with calculating the work function of various metals 
> (Au and Pt in particular) using the X.pbe-mt_fhi.UPF and X.pbe-n-nc.UPF 
> pseudo potentials.  Unlike in the example in WorkFct_example in PP I am 
> regularly getting a positive Fermi energy and a vacuum level which is lower 
> than the average level for the potential of the atoms.  Is this a case of 
> poor pseudo potential choice, a bug or user error?
>  
> Any advice would be appreciated,
>  
> Kind regards
>  
> Steven
>  
>  
> Dr. Steven Hepplestone
> Physics
> University of Exeter
> Stocker Road
> Exeter
> EX4 4QL
> Ext.: +44 (0)1392 723048
> Int.: 3048
>  
> ___
> Pw_forum mailing list
> Pw_forum@pwscf.org 
> http://pwscf.org/mailman/listinfo/pw_forum 
> 
-- 

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cant...@spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: http://people.na.infn.it/~cantele

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Re: [Pw_forum] Work function issues

[Giuseppe Mattioli]

Dear all
If you do not want to bother with potential realignment in slab calcuations of 
WF you can use the (very nice) new implementation of the ESM method in 
a vacuum-slab-vacuum framework.

The usage is very simple

assume_isolated = 'esm',
esm_bc='bc1',

and you find in the outdir some prefix.esm1 file containing all the desired 
quantities (charge density, a variety of potentials) averaged along the z 
axis of the cell.

#z (A)  Tot chg (e/A)  Avg v_hartree (eV)  Avg v_local (eV)  Avg v_hart+v_loc 
(eV)

As the method decouple the slab along z you can also treat polar interfaces 
(e.g. gold electrode + polar SAM) and obtain two nice, different, flat 
asymptotic values of the potential on the two sides of the slab, without using 
any dipole correction.

HTH
Giuseppe

On Friday, April 22, 2016 04:51:18 PM Giovanni Cantele wrote:
> Maybe it is neither a poor pseudo potential choice nor a bug or user error.
> 
> Using for example Au.pbe-mt_fhi.UPF  I get
> 
> Fermi level ~ 3.30 eV
> vacuum level ~ 8.48eV
> 
> with a plot similar to what you attach in a follow-up e-mail.
> That corresponds to a ~ 5.17 gold work function, not that far from literature 
> results, see, e.g., PHYSICAL REVIEW B 80, 235407 2009 .
> 
> Take care of slab thickness convergence issues as well as of the fact that a 
> more accurate calculation might require a bulk crystal calculation,
> see details in the above reported reference.
> 
> Giovanni
> 
> > On 21 Apr 2016, at 17:57, Hepplestone, Steven 
> >  wrote:
> > 
> > Dear all,
> > 
> > I am having difficulties with calculating the work function of various 
> > metals (Au and Pt in particular) using the X.pbe-mt_fhi.UPF and
> > X.pbe-n-nc.UPF pseudo potentials.  Unlike in the example in WorkFct_example 
> > in PP I am regularly getting a positive Fermi energy and a vacuum
> > level which is lower than the average level for the potential of the atoms. 
> >  Is this a case of poor pseudo potential choice, a bug or user error?
> > 
> > Any advice would be appreciated,
> > 
> > Kind regards
> > 
> > Steven
> > 
> > 
> > Dr. Steven Hepplestone
> > Physics
> > University of Exeter
> > Stocker Road
> > Exeter
> > EX4 4QL
> > Ext.: +44 (0)1392 723048
> > Int.: 3048
> > 
> > ___
> > Pw_forum mailing list
> > Pw_forum@pwscf.org 
> > http://pwscf.org/mailman/listinfo/pw_forum 
> > 


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   Giuseppe Mattioli
   CNR - ISTITUTO DI STRUTTURA DELLA MATERIA   
   v. Salaria Km 29,300 - C.P. 10
   I 00015 - Monterotondo Stazione (RM), Italy
   Tel + 39 06 90672836 - Fax +39 06 90672316
   E-mail: 
   http://www.ism.cnr.it/en/staff/giuseppe-mattioli/
   ResearcherID: F-6308-2012

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