[Pw_forum] Converting pseudopotentials from CPMD

[Axel Kohlmeyer]

On Fri, Nov 25, 2011 at 9:27 AM, Merlin Meheut
<merlin.meheut at get.obs-mip.fr> wrote:
> Dear pwscf users,
>
> I am trying to obtain consistent pseudopotentials to use in both CPMD and
> pwscf, precisely for O,H, Si and Li atoms.
> I therefore took pseudopotentials from CPMD and tried the cpmd2upf.x
> converter.
>
> I am however not sure of what I should do. In particular, I am not sure of
> the local reference state used in these pseudos.
> Does this have an influence on the conversion, or is that just an
> information written somewhere in comment in the UPF pseudopotential?
>  More generally, I am not sure of the recipes used to generate these
> pseudos, and in which
> extent they should be considered in the conversion. THe only information I
> have is inside the preamble of the pseudopotential files
> (Pseudopotential report), which is reproduced below:
>
> For example, for the Li atom, I attached the cpmd pseudopotential and here
> are the instructions I gave for conversion:
>
> $ ./cpmd2upf.x
> Input file > Li_MT_BLYP_NLCC.psp

i don't think that anybody every got the NLCC conversion
from CPMD to UPF working correctly. i remember i tried
several iterations back and forth with paolo many years
ago and then finally went the other route and regenerated
pseudopotentials with from the same settings with paulo's
atomic code and then converted the output to cpmd format
and UPF alike.


> amesh set to:  1.002086
>    ============================================================
>    |    Pseudopotential Report     Thu Aug 22 12:57:11 1996   |
>    ------------------------------------------------------------
>    |  s channel:                                              |
>    |  Atomic Symbol                   :   LI                  |
>    |  Atomic Number                   :   3                   |
>    |  Number of core states           :   1                   |
>    |  Number of valence states        :   1                   |
>    |  Exchange-Correlation Functional :                       |
>    |     Slater exchange :   .6667                            |
>    |     LDA correlation : Lee-Yang-Parr                      |
>    |     Exchange GC     : Becke (1988)                       |
>    |     Correlation GC  : Lee-Yang-Parr                      |
>    |  Electron Configuration :   N   L  Occupation            |
>    |                             1   S    2.0000              |
>    |                             2   S    1.0000              |
>    |  Full Potential Total Energy    -7.571372                |
>    |  Trouiller-Martins normconserving PP                     |
>    |     n    l        rc       energy                        |
>    |     2    S    2.2000      -.11501                        |
>    |     2    P    2.2000      -.11501                        |
>    |  Nonlinear core correction                               |
>    |  Core charge cutoff radius :   1.80000                   |
>    |  Number of Mesh Points :   575                           |
>    |  Pseudoatom Total Energy    -.205704                     |
>    ============================================================
>    |  P-channel taken from:                                   |
>    |     2    S    2.2000      -.21051                        |
>    |     2    P    2.2000      -.13639                        |
>    |     3    D    1.7031      -.13639                        |
>    |  Nonlinear core correction                               |
>    |  Core charge cutoff radius :   1.80000                   |
>    |  Number of Mesh Points :   575                           |
>    |  Pseudoatom Total Energy    -.106791                     |
>    ============================================================
> lmax to use. (max. 1) > 1
> l local (max. 1) > 0
> Wavefunction # 1: label, occupancy > 2S, 1.0
> Wavefunction # 2: label, occupancy > 2P, 0.0
> Pseudopotential successfully converted
> Output PP file in UPF format :  Li_MT_BLYP_NLCC.psp.UPF
> *** PLEASE TEST BEFORE USING!!! ***
> review the content of the PP_INFO fields
>
>
> As you can see in the comment of the cpmd potential, the pseudopotential
> contains potentials (and wavefunctions) for 2S and 2P,
> with the energy of 2P fixed at the same value that 2S.

never trust those comments in CPMD pseudopotentials.
the atomic code creates bogus entries in there (and
nobody seemed to care to fix that issue) and some
people "fix" them afterwards, others don't and some
actually "fix" those tables incorrectly. several potentials
also mix results from different calculations and then
the comments can be completely bogus.

> I am not sure of what recipe it corresponds to: is that some sort of
> Hamann's approach?

the atomic code shipped with CPMD is based on
hamann's code, but heavily hacked.

> Of course, I could test these converted pseudopotentials, but I would like
> to be aware of potential problems before.

i would be very, *very* careful. particularly
on pseudopotentials with NLCC. i suspect,
but never found proof, that there are some
cases where a bug in the atomic code related
to NLCC is compensated by a corresponding
bug in the CPMD code.

axel.

> I would be very thankfull for any help,
>
> Best regards,
>
> Merlin Méheut
>
> --
> Merlin Méheut
> adresse labo:
> Géosciences Environnement Toulouse
> OMP   - Université Paul Sabatier
> 14 avenue Edouard Belin
> 31400 Toulouse
> FRANCE
> tel: (+33) 5 61 33 26 21
> adresse personelle:
> 3 rue du Puits Vert
> 31000 Toulouse
> port: (+33) 6 34 67 57 02
> pseudo skype: quantification
>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
>



-- 
Dr. Axel Kohlmeyer
akohlmey at gmail.com  http://goo.gl/1wk0

College of Science and Technology
Temple University, Philadelphia PA, USA.