[Pw_forum] Converting pseudopotentials from CPMD
Merlin Meheut
merlin.meheut at get.obs-mip.fr
Fri Nov 25 18:08:19 CET 2011
Dear Axel,
So you say you used ld1.x to generate both UPF and cpmd
pseudopotentials, or did you use another software?
In INPUT_LD1.txt they say this is still an "experimental feature"...
Which software would you recommend to generate both pseudopotentials
consistently?
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?
$ ./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
>>>>
>>>>
>>>> _______________________________________________
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>>>>
>>>>
>>>
>>
>> --
>> 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
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