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

[jqhuang16b at imr.ac.cn]

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 (www.max-centre.eu/quantum-espresso)
> >>> users mailing list users at lists.quantum-espresso.org
> >>> https://lists.quantum-espresso.org/mailman/listinfo/users
> >>> 
> >> 
> >> -- 
> >> 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)
> > 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)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users