[QE-users] users Digest, Vol 166, Issue 1
Anish Das
anishdas39 at gmail.com
Sat May 1 12:40:43 CEST 2021
Dear Dr. Hanghui Chen
You have been such an expert in QE and i am just a beginner in QE, so my
comment may not be helpful to you. However, I still want to share my
little experience with the calculation of charged supercells. Charged
supercell basically has an odd number of electrons than the
neutral counterpart (In terms of chemistry language it is like a single
cation or anion). In case of negatively charged supercell (like anion)
after free relaxation i found that the cell lengths are expanded than the
neutral case, which is acceptable because in case of anion, the radius of
an atom is larger than the radius of neutral atom. Few days ago I also did
some calculations of negatively charged supercells with and without
relaxation. I found that for non relaxed charged supercell I found
pretty bad results, 1) the formation energy is wrong (also after applying
FNV correction scheme), 2) I could not properly sort out the defects
states, 3) Fermi level shifted absurdly and showing metallic n-type
behavior and , 4) the pressure of the cell is also very high (5.06 kbar).
So I always relax the charged supercell.
During the relaxation of charged supercell sometimes we also found very
prominent change in the neighbouring co-ordination near the defect. I also
found that energy of the relaxed charged supercell is sometimes over
estimated, while calculating the formation energy. To correct that
formation energy of the charged supercell I generally apply the FNV scheme
(remove spurious charge interaction between periodic image + band
alignment) and I get good results.
On Sat, 1 May 2021 at 15:30, <users-request at lists.quantum-espresso.org>
wrote:
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> Today's Topics:
>
> 1. relaxation of a charged system (Hanghui Chen)
> 2. Re: how to add library libfabric.so.1 (Jota Be)
> 3. Re: convergence NOT achieved after 100 iterations for
> spin-orbit coupling (SOUMYAKANTA PANDA)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 30 Apr 2021 22:11:26 +0800
> From: Hanghui Chen <chenhanghuipwscf at gmail.com>
> To: users at lists.quantum-espresso.org
> Subject: [QE-users] relaxation of a charged system
> Message-ID:
> <CAOE2MOzBzYm8n5hnMCpeXJ=TNSs1M504voDF=
> xXkQa_M-FY6mw at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Dear QE developers,
> I have been using Quantum Espresso for more than a decade and recently
> a paper (PRB 91, 024107 (2015)) caught my attention, which shows that the
> total energy, pressure and cell relaxation are ill-defined in charged
> systems (even if a compensating charge background is present). The paper
> shows that the total energy and pressure of a charged system depend on the
> average electrostatic potential convention, and thus is code-dependent (QE,
> ABINIT and VASP use different conventions).
> I think the paper is theoretically correct. However in practice, we
> have recently tested doped ferroelectric materials using both QE and VASP.
> In this charged system, we find both QE and VASP yield qualitatively
> consistent structural properties.
> Since relaxation of a charged system is very common in literature using
> QE or VASP (e.g. PRL 109, 247601 (2012) and many others), I am wondering
> whether the relaxed structure of a charged system from QE is reliable.
> According to PRB 91, 024107, it is not legitimate to do cell relaxation of
> a charged system. However both QE and VASP do allow to calculate total
> energy and perform cell relaxation in a charged system. And from
> literature, it seems that the relaxed structure of a charge system from QE
> or VASP calculations is "not too wrong".
> So what is your insight on this issue? Shall we prohibit ourselves from
> doing cell relaxation of a charged system in QE, or can we still use the
> standard procedure but with the caution that the optimized structure of a
> charged system from QE might not be accurate (due to the QE convention of
> average electrostatic potential)?
> Thank you very much.
>
> Dr. Hanghui Chen
> Department of Physics
> NYU Shanghai and New York University
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> Message: 2
> Date: Fri, 30 Apr 2021 07:57:09 -0700
> From: Jota Be <jotabe1789 at gmail.com>
> To: users at lists.quantum-espresso.org
> Subject: Re: [QE-users] how to add library libfabric.so.1
> Message-ID:
> <
> CALMYQAv_0u-5kCAron8Ugo+J6-Sn0pCChwGr+ho_2TwacGkHmA at mail.gmail.com>
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>
> Thank you for your help!
> My issue is that I wasn't sourcing. I haven't compiled code in a long time.
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> Message: 3
> Date: Sat, 1 May 2021 13:06:36 +0530
> From: SOUMYAKANTA PANDA <sp57 at iitbbs.ac.in>
> To: Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
> Subject: Re: [QE-users] convergence NOT achieved after 100 iterations
> for spin-orbit coupling
> Message-ID:
> <
> CALjPOz2Hm-jsQYEc_5V_FGiNvNBLEqOhcay-iCxN_oTj+bQTkA at mail.gmail.com>
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>
> Hi Reem Abdel-Kader Ibrahim
> It is very difficult to converge spin orbit based calculations ( very very
> difficult) by taking GGA based potentials. Try to converge it by taking LDA
> type flavor ( pz potentials) and in relaxation avoid soc to get quick
> convergence. You can add spin-orbit in scf calculations with LDA flavor.
> Try to use small value of mix beta.
> Regards,
> Soumyakanta Panda
> Research Scholar
> Nano Magnetism and Magnetic Materials Laboratory
> IIT Bhubaneswar, India
>
>
> On Sat, May 1, 2021 at 12:58 PM SOUMYAKANTA PANDA <sp57 at iitbbs.ac.in>
> wrote:
>
> > Hi Reem Abdel-Kader Ibrahim
> > It is very difficult to converge spin orbit based calculations ( very
> very
> > difficult) by taking GGA based potentials. Try to converge it by taking
> LDA
> > type flavor ( pz potentials) and in relaxation avoid soc to get quick
> > convergence. You can add spin-orbit in scf calculations with LDA flavor.
> > Try to use small value of mix beta.
> >
> >
> >
> > Regards,
> > Soumyakanta Panda
> > Research Scholar
> > Nano Magnetism and Magnetic Materials Laboratory
> > IIT Bhubaneswar, India
> >
> >
> > On Fri, Mar 12, 2021 at 4:48 PM Paolo Giannozzi <p.giannozzi at gmail.com>
> > wrote:
> >
> >> On Fri, Mar 12, 2021 at 11:46 AM Kazume NISHIDATE <
> nisidate at iwate-u.ac.jp>
> >> wrote:
> >>
> >> > - nspin:- the noncolin and nspin are conflicting flags, both should
> >>> > not be present within the same calculation
> >>>
> >>
> >> very true, but in practice there is no problem if both are present, as
> >> long as they are consistent.
> >>
> >> Paolo
> >> --
> >> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> >> Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
> >> Phone +39-0432-558216, fax +39-0432-558222
> >>
> >> _______________________________________________
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> >> https://lists.quantum-espresso.org/mailman/listinfo/users
> >
> >
>
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> End of users Digest, Vol 166, Issue 1
> *************************************
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--
Anish Das
M.Tech. (Materials science and Engineering)
Materials science centre
IIT Kharagpur, India
Mob. +91-9800420192
email id: anishdas39 at gmail.com
Google Scholar: https://goo.gl/d2hW9u
ResearchGate: *https://goo.gl/MY55ee <https://goo.gl/MY55ee>*
LinkedIn: https://goo.gl/2ckhSB
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