[Pw_forum] Praseodymium Pseudopotential(s)

[Vo, Trinh (388C)]

Dear Stefano,

Since I have the same interest of generating a PP for an rare-earth element
(Yb), if you don't mind, could you send me the input that you used to
generate PP for Ce.  I am trying to generate a PP for Yb, using QE, but I
have failed so far.  I would like to look at the input file generating Ce PP
to have an idea, since they are of the same Lanthanide family.

Thank you very much,

Trinh Vo
CalTech/JPL
 


On 8/26/10 6:11 PM, "w2agz" <w2agz at pacbell.net> wrote:

> Hi Stefano(s),
> 
> Thanks for your feedback.  I wouldn't be surprised that praseodymium would
> have similar issues as cerium.  Ce is [Xe]4f 5d 6s2  and Pr [Xe]4f3 6s2,
> and, as I mentioned below, Pr-1237 is the only lanthanide copper oxide
> perovskite that doesn't superconduct.  (The Ce copper oxides don't form in
> the same perovskite structure).
> In any event, your comment that correlations in these materials are very
> cogent, and that employing a LDA+U framework is mandatory.
> 
> You mentioned "...posting pseudos on the web"...is it possible for QE users
> to submit PPs they've found handy to the QE Wiki?  I constructed a PP
> favoring the Cu 3d9 4s2 configuration which I found very useful for
> calculating ground state antiferromagnetic properties of CuO, both as
> tenorite and tetragonal rocksalt.  I generated it using the QE PP code, and
> could make it available (no guarantees, of course!).
> 
> -Paul
> 
> 
> 
> --------------------------------------------------
> From: "Stefano de Gironcoli" <degironc at sissa.it>
> Sent: Thursday, August 26, 2010 12:21 AM
> To: "PWSCF Forum" <pw_forum at pwscf.org>
> Cc: "Stefano Fabris" <fabris at democritos.it>
> Subject: Re: [Pw_forum] Praseodymium Pseudopotential(s)
> 
>> Dear Paul,
>>   I have no experience with Praseodymium but have been involved in some
>> calculations with Cerium that shares with it the mixed valence nature.
>>   Stefano Fabris (here in cc) generated a couple of pseudopotentials
>> that were successfully used in a number of studies. He can send you
>> more info... and possibly post the pseudos on the web...
>>   Beware however that in order to obtain even qualitatively sensible
>> results with Ce (and I guess also with Pr)  DFT+U or a similarly
>> self-interaction corrected scheme is mandatory.
>>   best regards,
>>          Stefano de Gironcoli
>> 
>> 
>> w2agz wrote:
>>> Ciao Tutti (especially Paolo, Mateo etc.),
>>> 
>>> 
>>> 
>>> OK, I've been away for a while, busy with energy issues and trying to
>>> understand why Alex Mueller may have been on the right track wrt to
>>> explaining why high temperature superconductivity manifests in the copper
>>> oxide perovskites.  PW_FORUM is not the right place to "advertize" one's
>>> publications, but I owe much to the QE community and its creators and
>>> contributors.  Contact me if you're interested in further info.
>>> 
>>> 
>>> 
>>> The reason for this posting is as follows:
>>> 
>>> (1)    I'd like to investigate via QE-DFT the "properties" of several Pr,
>>> alkaline earth-oxide perovskites, and thus need to have an appropiate Pr
>>> pseudopotential, one that would be compatible with the PP library of QE.
>>> 
>>> (2)    Browsing the QE, Vanderbilt, Opium, Haber and Martins sites
>>> (US-PS, NC-PS), I could find "none" that were pregenerated.
>>> 
>>> (3)    Therefore, I may be "on my own," and would appreciate advice:
>>> 
>>> a.       Is the community aware of any suitable Pr PPs I could obtain and
>>> use?
>>> 
>>> b.      If not, I'd appreciate advice on how to generate my own, using
>>> either the "famous" ld1.x,  or a suitable equivalent
>>> 
>>> c.   Does anyone know about or use the "Octopus" site
>>> (http://www.tddft.org/programs/octopus)
>>> 
>>> (4)    Pr is a particular pernicious element ([Xe] 4f3-6s2) .  Simply
>>> put, it can be either 3+ or 4+.or somewhere in between - the 4f states
>>> are known to hybidize extensively.  Studies I did at IBM on the Pr-1237
>>> system indicated its ground quantum state may be in some sort of "heavy
>>> fermion" configuration.  Think about it.  Why is not Pr-1237
>>> superconducting.or even metallic, even though its crystal structure is
>>> nearly identical to Y-1237?  That's the most unsolved mystery of 20th
>>> century condensed matter physics.next to why the copper oxide perovskites
>>> are superconducting at all.
>>> 
>>> 
>>> 
>>> Finally, I remind all of the wisdom of David Vanderbilt's remark,
>>> something to the effect, "Pseudopotential generation is a black art."
>>> 
>>> 
>>> 
>>> Paolo, can you work your magic?
>>> 
>>> 
>>> 
>>> Ciao, -Paul
>>> 
>>> 
>>> ------------------------------------------------------------------------
>>> 
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>> 
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