[QE-users] Issue on LDA+U test calculation on Gd

[Andrea Dal Corso]

On Mon, 2020-02-10 at 16:21 +0000, Timrov Iurii wrote:
> Dear Giovanni,
> 
> 
> > I’ve browsed the PW/src/offset_atom_wfc.f90 routine. It seems (that
> > is what I have understood) that while in Modules/set_hubbard_l.f90
> > it is set
> 
> hubbard_l = 3  for that atomic species, in the pseudo potential file
> (see e.g. 
> http://www.quantum-espresso.org/upf_files/Gd.pbe-spdn-kjpaw_psl.1.0.0.UPF
> )
> the l=3 wave function is not found.
> > The atomic configuration of Gd is Xe 4f7 5d1 6s2.
> 
> 
> I would try to use the recommended pseudo from the SSSP library. For
> Gd, the recommended pseudo is from the Wentzcovitch library. I do not
> know if f electrons are included, though, one has to check.
> 
> 
> > i) it is sufficient to solve the problem or wrong to set hubbard_l
> > = 2 in Modules/set_hubbard_l.f90?
> > Should the Hubbard U be more important for those l=3 electronic
> > states than for l=2 states?
> 
> 4f and 5d channels are both partially occupied, so I presume that one
> should try to put U on both channels (but this is currently not
> possible in QE). So, by default the f channel is used for Gd in QE.
> It is not obvious (at least for me) though whether putting U on 5d
> would be important for Gd. One should investigate the PDOS and see
> where the contributions from 4f and 5d are located (at the LDA or GGA
> level), and on the basis of this information decide to which channel
> U should be applied.
> 
> > ii) more importantly (sorry for the basic question, I’v never
> > considered systems with f electrons): why f electrons are not
> > considered in the pseudo file?
> 
> You have chosen the PP which indeed does not contain the f states.
> But in the PSlibrary there are pseudos of Gd containing f electrons,
> so you can try those. It is better to ask Andrea Dal Corso why f
> states were not included in some versions of pseudos.
> 
The PPs of Lanthanides with f states in the core can be useful if you
are not interested in magnetic properties and for application were the
f occupation is not changing. They have been used sometimes in the
literature and are provided for those that are interested in these
cases.

Andrea

> Best regards,
> Iurii
> 
> 
> 
> --
> Dr. Iurii Timrov
> Postdoctoral Researcher
> STI - IMX - THEOS and NCCR - MARVEL
> Swiss Federal Institute of Technology Lausanne (EPFL)
> CH-1015 Lausanne, Switzerland
> +41 21 69 34 881
> http://people.epfl.ch/265334
> ________________________________
> From: users <users-bounces at lists.quantum-espresso.org> on behalf of
> Giovanni Cantele <giovanni.cantele at spin.cnr.it>
> Sent: Monday, February 10, 2020 4:51:11 PM
> To: Quantum ESPRESSO users Forum
> Subject: [QE-users] Issue on LDA+U test calculation on Gd
> 
> Dear all,
> 
> I’m trying to make a test calculation of a crystal containing the Gd
> atom. I use the DFT+U scheme.
> However, as the program starts, I’ve immediately facing the following
> error:
> 
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> %%%%%%%%%
>      Error in routine offset_atom_wfc (2):
>      wrong offset
>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> %%%%%%%%%%
> 
> 
> I’ve browsed the PW/src/offset_atom_wfc.f90 routine. It seems (that
> is what I have understood) that while in Modules/set_hubbard_l.f90 it
> is set
> hubbard_l = 3  for that atomic species, in the pseudo potential file
> (see e.g. 
> http://www.quantum-espresso.org/upf_files/Gd.pbe-spdn-kjpaw_psl.1.0.0.UPF
> )
> the l=3 wave function is not found.
> The atomic configuration of Gd is Xe 4f7 5d1 6s2.
> 
> So my question is:
> 
> i) it is sufficient to solve the problem or wrong to set hubbard_l =
> 2 in Modules/set_hubbard_l.f90?
> ii) more importantly (sorry for the basic question, I’v never
> considered systems with f electrons): why f electrons are not
> considered in the pseudo file?
> Should the Hubbard U be more important for those l=3 electronic
> states than for l=2 states?
> 
> Thanks for any answer you could provide.
> 
> Giovanni
> 
> 
> 
> --
> 
> Giovanni Cantele, PhD
> 
> CNR-SPIN
> c/o Dipartimento di Fisica
> Universita' di Napoli "Federico II"
> Complesso Universitario M. S. Angelo - Ed. 6
> Via Cintia, I-80126, Napoli, Italy
> 
> e-mail: giovanni.cantele at spin.cnr.it<mailto:
> giovanni.cantele at spin.cnr.it>
>             gcantele at gmail.com<mailto:gcantele at gmail.com>
> Phone: +39 081 676910
> Skype contact: giocan74
> Web page: https://sites.google.com/view/giovanni-cantele
> 
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-- 
Andrea Dal Corso                    Tel. 0039-040-3787428
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