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

[Lorenzo Paulatto]

> 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
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-- 
Lorenzo Paulatto - Paris