[Pw_forum] Converting pseudopotentials from CPMD
Axel Kohlmeyer
akohlmey at gmail.com
Fri Nov 25 18:34:36 CET 2011
On Fri, Nov 25, 2011 at 12:08 PM, Merlin Meheut
<merlin.meheut at get.obs-mip.fr> wrote:
>
> Dear Axel,
>
> So you say you used ld1.x to generate both UPF and cpmd pseudopotentials, or
> did you use another software?
i used a different software and that was many years ago.
> In INPUT_LD1.txt they say this is still an "experimental feature"...
>
> Which software would you recommend to generate both pseudopotentials
> consistently?
i have no recommendation. i have not created
any pseudopotentials since then and thus have
no idea what shape the various programs are in.
> I must admit I am not very confident with using ld1, but if it does the job
> I should be able to handle it
> (with a little bit of help probably...) .
>
> Another question: I have a very simple case, the O pseudopotential
> (attached), which seems quite straightforward to convert
> (with a 2s2 2p4 configuration, and no other l in the potential):
> do you think that with these commands the result should be correct? Even if
> I do not give the local projector originally used?
the only way to know if the conversion is correct is
to run some test calculations. i don't know what you
mean by " I do not give the local projector originally used?"
axel.
>
> $ ./cpmd2upf.x
> Input file > O_MT_GIA_BLYP
> Oxygen 2s2 2p4 BLYP rc= 1.05 1.05
> lmax to use. (max. 1) > 1
> l local (max. 1) > 1
> Wavefunction # 1: label, occupancy > 2S, 2.0
> Wavefunction # 2: label, occupancy > 2P, 4.0
> Pseudopotential successfully converted
> Output PP file in UPF format : O_MT_GIA_BLYP.UPF
>
> Thanks in advance,
>
> Merlin Méheut
>
>
>
> On 25/11/2011 17:24, Axel Kohlmeyer wrote:
>>
>> On Fri, Nov 25, 2011 at 11:02 AM, Merlin Meheut
>> <merlin.meheut at get.obs-mip.fr> wrote:
>>>
>>> Hi Axel,
>>>
>>> Thanks for your help,
>>>
>>> To have some understanding on the problem, I compared the original and
>>> converted pseudopotential files: if they are not exactly the same,
>>> the spatial grid (<PP_R> in the UPF file, first column of all fields for
>>> CPMD format), the wavefunction values (for 2S and 2P:<PP_PSWFC>
>>> in the UPF file,&WAVEFUNCTION in CPMD) , and the NLCC fields
>>> (<PP_NLCC> in the UPF file,&NLCC in CPMD) are exactly the same in both
>>> files. I was not too much worried about the nlcc correction, for this
>>> reason...
>>>
>>> However, for the rest of the file, the CPMD file has only a&POTENTIAL
>>> field wit 2S and 2P potentials, whereas the UPF file have<PP_RAB> ,
>>> <PP_LOCAL>, and<PP_NONLOCAL> fields, and I do not see any agreement
>>> between the two. What should be the connection?
>>
>> with CPMD potentials you have to indicate the local potential
>> in the CPMD input file and then the kleinman-bylander procedure
>> is done internally in CPMD, whereas in UPF this is already
>> encoded in the pseudopotential. CPMD also offers to use
>> gauss-hermite integration instead of kleinman-bylander
>> (more expensive, but may be needed to avoid ghost
>> states, e.g. for transition metals).
>>
>>> The cpmd file seems quite simple, with two wavefunctions, two potentials
>>> and one nlcc field. Where is the difficulty of the conversion?
>>> How are the two formats differing for the potentials? Since I have the
>>> same values for the wavefunctions, spatial grid and nlcc,
>>> shouldn't I have the same also for potentials? Maybe this is related to
>>> a wrong choice for the local part?
>>
>> the problems are related to having to anticipate correctly
>> the transformations, regridding, and re-normalizations that
>> CPMD is doing. add to that that the occasional factor 2
>> since CPMD uses hartree atomic units while Q-E uses
>> rydberg atomic units.
>>
>>> By the way, I began by the most difficult case: the O, H and Si
>>> pseudopotentials I have do not contain nlcc corrections:
>>> do you think that I can trust the conversion, even if I do not give the
>>> correct local l?
>>
>> it is always better to start with the easiest case and
>> make sure that it works. i am not saying that it is
>> impossible what you want to do, but one has to make
>> fairly detailed tests and know how the potentials were
>> created to fill in the blanks. for exactly that reason,
>> i found it simpler to start from a consistent atomic
>> code that can produce both, CPMD format and UPF
>> output, and then feed those potentials to both codes
>> to see, if they can work well.
>>
>>> My problem for re-generating a pseudo is that I am not quite confident
>>> in which recipe to use... Especially for Li....
>>
>> Li is a quite difficult case. i think the NLCC version
>> only works well for metallic Li and you may be better
>> off to do a "semi-core" style potential for ionic Li.
>>
>>> Since you say cpmd comments can't be trusted, do you think rc are all
>>> bogus?
>>
>> cannot trusted means, that you don't know. some are correct,
>> some are bogus. it all depends on who created the potential
>> and what this person assumed about how and by whom the
>> potential will be used. most are more-or-less accurate.
>> often you can tell bogus entries if the energy eigenvalue is
>> identical to the previous state. but i also have seen potentials,
>> where the comment section was that of a completely different potential...
>>
>> that is what i mean by unreliable... you can't really know from the file.
>>
>> axel.
>>
>>> Best regards,
>>>
>>> Merlin Méheut
>>>
>>>
>>>
>>> On 25/11/2011 16:03, Axel Kohlmeyer wrote:
>>>>
>>>> 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
>>>>>
>>>>>
>>>>
>>>
>>> --
>>> 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
>>>
>>
>>
>
>
> --
> 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.
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