[QE-users] phonon dispersion relation from the full IFCs

Sat Jan 11 16:26:34 CET 2020

You're clearly doing dinner wrong, but you're not providing enough
information to say what. I would recommend you study the code and
literature and understand how one comes from the other before changing
parameters. P.s. alpha is an inverse length.

Regards

-- 
Lorenzo Paulatto

On Sat, 11 Jan 2020, 10:50 , <jqhuang16b at imr.ac.cn> wrote:

> Thank you, sir. I have another confusion now.
> The long-range dynamical matrix should not change too much if I reset alph
> to a larger number, given that it is convergent.
> However, I set alph= 2.0d0 and obtain a very different long-range
> dynamical matrix.
> Where is the problem?
>
>
> > -----原始邮件-----
> > 发件人: "Stefano Baroni" <baroni at sissa.it>
> > 发送时间: 2020-01-11 02:47:40 (星期六)
> > 收件人: "Quantum ESPRESSO users Forum" <users at lists.quantum-espresso.org>
> > 抄送:
> > 主题: Re: [QE-users] phonon dispersion relation from the full IFCs
> >
> > 1.0 tons is 1000000000 times larger than 1.0 mg. A very large number
> indeed! SB
> >
> > --
> > Stefano Baroni, Trieste -- swift message written and sent on the go
> >
> > > On 10 Jan 2020, at 18:03, jqhuang16b at imr.ac.cn wrote:
> > >
> > > Thank you so much, professor. I really appreciate your scrupulous
> reply over and over again.
> > > In the QE code(subroutine rgd_dyn) of computing the rigid-ion
> (long-range) term, it is commented that
> > > "Only the G-space term is implemented: the Ewald parameter alpha must
> be large enough to have negligible r-space contribution".
> > > But in the following value assignment, alph= 1.0d0, not a very large
> number.
> > > I think such a value will not make the real-space term vanish in the
> Ewald summation.
> > > How to understand this?
> > >
> > >
> > >> -----原始邮件-----
> > >> 发件人: "Lorenzo Paulatto" <paulatz at gmail.com>
> > >> 发送时间: 2020-01-10 17:19:48 (星期五)
> > >> 收件人: users at lists.quantum-espresso.org
> > >> 抄送:
> > >> 主题: Re: [QE-users] phonon dispersion relation from the full IFCs
> > >>
> > >>> Is it equivalent to the regular adopted Ewald summation method in
> mathematics?
> > >>
> > >> I think you forgot to attach the paper in question...
> > >>
> > >> That said, if there is not lo-to splitting, there are no effectiv
> > >> charges and no long-range interaction. Than there is no problem doing
> > >> Fourier interpolation.
> > >>
> > >> 2D is a bit special, but the QE code has special techniques to deal
> with
> > >> 2D phonon interpolation, I think it is explained in Phys. Rev. B 94,
> 085415
> > >>
> > >> cheers
> > >>
> > >>>
> > >>> With thanks and best regards !
> > >>> Happy New Year !
> > >>>
> > >>>
> > >>> --
> > >>> Jian-qi Huang
> > >>>
> > >>> Magnetism and Magnetic Materials Division
> > >>> Institute of Metal Research
> > >>> Chinese Academy of Sciences
> > >>> 72 Wenhua Road, Shenyang 110016, China
> > >>>
> > >>> email:jqhuang16b at imr.ac.cn
> > >>>
> > >>>> -----原始邮件-----
> > >>>> 发件人: "Lorenzo Paulatto" <paulatz at gmail.com>
> > >>>> 发送时间: 2020-01-09 03:56:21 (星期四)
> > >>>> 收件人: users at lists.quantum-espresso.org
> > >>>> 抄送:
> > >>>> 主题: Re: [QE-users] phonon dispersion relation from the full IFCs
> > >>>>
> > >>>>> Thank you for reply, professor. I understand the regular routine
> > >>>>> implemented in QE where the long-range contribution is added in
> > >>>>> reciprocal space. My point is can I get the correct dynamical
> matrix
> > >>>>> just by making inverse Fourier transformation of the
> full(short+long)
> > >>>>> IFCs in a large real space?
> > >>>>>
> > >>>>
> > >>>> The dynamical matrix at Gamma is discontinuity with respect to the
> > >>>> points nearby, which would make any Fourier transform impossible to
> > >>>> converge.
> > >>>>
> > >>>> I think you should explain WHY you want to do this, and you may get
> some
> > >>>> better answer.
> > >>>>
> > >>>> In practice, if I was obliged at gunpoint, I would replace the
> dynamical
> > >>>> matrix file at Gamma (typically dyn1) with one computed very close
> to
> > >>>> Gamma, let's say q=0.001,0,0. Edit the file to trick q2r into
> thinking
> > >>>> that it was done at exactly Gamma, and see was comes out.
> > >>>>
> > >>>> If the material has a non-analytic term (i.e. the long range term
> > >>>> depends on the direction), this will definitely not work.
> Otherwise, you
> > >>>> may get something decent.
> > >>>>
> > >>>>
> > >>>> cheers
> > >>>>
> > >>>>
> > >>>>
> > >>>> --
> > >>>> Lorenzo Paulatto - Paris
> > >>>> _______________________________________________
> > >>>> Quantum ESPRESSO is supported by MaX (
> www.max-centre.eu/quantum-espresso)
> > >>>> users mailing list users at lists.quantum-espresso.org
> > >>>> https://lists.quantum-espresso.org/mailman/listinfo/users
> > >>> _______________________________________________
> > >>> Quantum ESPRESSO is supported by MaX (
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> > >>>
> > >>
> > >> --
> > >> Lorenzo Paulatto - Paris
> > >> _______________________________________________
> > >> Quantum ESPRESSO is supported by MaX (
> www.max-centre.eu/quantum-espresso)
> > >> users mailing list users at lists.quantum-espresso.org
> > >> https://lists.quantum-espresso.org/mailman/listinfo/users
> > > _______________________________________________
> > > Quantum ESPRESSO is supported by MaX (
> www.max-centre.eu/quantum-espresso)
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> >
> > _______________________________________________
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> _______________________________________________
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