# [Pw_forum] Pseudo-potential testing

Gabriele Sclauzero sclauzer at sissa.it
Mon May 30 10:08:04 CEST 2011

```Hello,

Il giorno 27/mag/2011, alle ore 20.05, Tram Bui ha scritto:

> Dear Gabriele,
>     Thank you for your respond. Just to make sure that I'm understanding your answer correctly, below is a shortcut on the output file of my PP testing:
>
> ---------------------- Testing the pseudopotential ----------------------
>
>
>      scalar relativistic calculation
>
>      atomic number is 55.00   valence charge is  1.00
>      dft =PBE   lsd =0 sic =0 latt =0  beta=0.20 tr2=1.0E-14
>      mesh =1251 r(mesh) = 101.25750 xmin = -7.00 dx = 0.01250
>
>      n l     nl             e AE (Ry)        e PS (Ry)    De AE-PS (Ry)
>      1 0     6S   1( 0.50)       -0.17728       -0.17238       -0.00490
>      2 1     6P   1( 0.50)       -0.07657       -0.07687        0.00030
>      3 2     5D   1( 0.00)       -0.05580       -0.05081       -0.00499
>
>      eps = 8.5E-15  iter = 22
>
>      Etot =  -15573.817276 Ry,   -7786.908638 Ha, -211892.560039 eV
>      Etotps =    -0.217507 Ry,      -0.108753 Ha,      -2.959329 eV
>      dEtot_ae =       0.049938 Ry
>      dEtot_ps =       0.048795 Ry,   Delta E=       0.001144 Ry
>
>      Ekin =       0.080184 Ry,       0.040092 Ha,       1.090963 eV
> So I should look at the "De AE-PS (Ry)", which is the difference in the eigenvalues? or the "Delta E"? I assume it is the Delta E based on your respond. But am I correct?

I would say that you should look at both, but what Paolo was referring to in the guide is the second thing.
The Delta E looks fair to me, that's what you can expect from standard USPP. The difference in the eigenvalues seems instead a bit too large, maybe you can still improve a bit the quality of the PP.

HTH

GS

>
> Regards,
> Tram
>
> On Thu, May 26, 2011 at 2:16 AM, Gabriele Sclauzero <sclauzer at sissa.it> wrote:
>
> Il giorno 26/mag/2011, alle ore 01.00, Tram Bui ha scritto:
>
>> Dear Paul,
>>        In the file that I have attached here (Paul's note on PP generation), under section 3.10: checking for transferability, you have mentioned about the:"The error on total energy diﬀerences
>> between PP and AE results gives a feeling on how good the PP is." Do you mean the difference in AE and PP eigenvalues?
>
> No, I think here Paolo "Paul" Giannozzi really meant what you understood first, but you didn't get it in the correct way.
> You should really compare total energy differences, which means:
> E_2(AE) - E_1(AE)    versus   E_2(PS) - E_1(PS)
> where 1 and 2 label two different electronic configurations, and NOT
> E_1(PS)  versus  E_1(AE)
> as you are probably trying to do.
>
>> because I saw the Etot and Etotps are huge difference
>
> This is often the case, given the high degree of freedom in the choice of PP parameters (especially for the local potential, I suppose).
>
>> but their eigenvalue (e, Ry) are closed.
>
> Indeed this is how it should be, since the modern PP are designed to reproduce the scattering properties of the AE atomic potential as best as possible.
>
>>
>> Dear QE users,
>>      I'm trying to test the Cs' US PP with reference configuration of :[Xe] 6s1 5d0 6p0. To test the PP, I'm using these five configuration (just by guessing):
>>      configts(1)= '6s1 6p0 5d0'
>>      configts(2)= '6s0.5 6p0.5 5d0'
>>      configts(3)= '6s0.5 6p0 5d0.5'
>>      configts(4)= '6s0 6p1 5d0'
>>      configts(5)= '6s0 6p0 5d1'
>> My questions are:
>>  - how to choose the configurations for PP testing based on the reference one? is there a strategy or some sort?
>
> Use some reasonable configurations (remove or add one electron, or a fraction of it, move one or more electrons between different orbitals, ...).
> The choice may also be driven by the class of materials that you are going to study (e.g. ionic crystals).
>
>>  - how many configurations are enough for the test?
>
> That's up to you... 5 look enough for me. Don't forget to do some testing with the solid state code (e.g. bond distance of dimers, lattice constant of simple solids...).
>
>
> HTH
>
>
> GS
>
>>
>> Thank you very much,
>>
>> Tram Bui
>>
>> M.S. Materials Science & Engineering
>> trambui at u.boisestate.edu
>>
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>
>
> § Gabriele Sclauzero, EPFL SB ITP CSEA
>    PH H2 462, Station 3, CH-1015 Lausanne
>
>
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>
>
>
> --
> Tram Bui
>
> M.S. Materials Science & Engineering
> trambui at u.boisestate.edu
>
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
PH H2 462, Station 3, CH-1015 Lausanne

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