Hello,

`in addition to what Gavin wrote, I'd remark that the implementation of`

`finite q AC conductivity (which is simply related to the dielectric`

`function) should not be difficult. Instead of taking (2.17) in`

https://arxiv.org/pdf/cond-mat/0402523v1.pdf

`you'd use Eq. 2.15 before the limit in q is taken, that's all. This is a`

`standard Kubo formula result (for conductivity or epsilon). However, you`

`should first sit back and think how large the q of interest will be. If it`

`is much smaller than any reasonable k-mesh finesse (I mean \Delta k`

`between two adjacent k-points) then you are out of luck.`

Karel --- x --- dr. Karel Vyborny Fyzikalni ustav AV CR, v.v.i. Cukrovarnicka 10 Praha 6, CZ-16253 tel: +420220318459 Date: Mon, 23 May 2016 06:25:56 -0600 From: Gavin Abo <gs...@crimson.ua.edu> To: ben amara imen <imen.benama...@gmail.com> Cc: Karel Vyborny <vybor...@fzu.cz> Subject: Re: [Wien] imaginary dielectric function In the article by Ambrosch-Draxl et al. [ https://arxiv.org/pdf/cond-mat/0402523v1.pdf [arxiv.org] ], you can see on page 26: Furthermore, for the high energy photons the q = 0 limit is not justified

`any more and thus a finite momentum transfer should be considered in`

`future`

work. I think that future work for q not equal to zero was never implemented for WIEN2k. I believe that is because they started working on their own DFT program called EXCITING [ https://en.wikipedia.org/wiki/EXCITING [en.wikipedia.org] ].

`If you look on the webpage for the elk branch [`

`http://elk.sourceforge.net/`

[elk.sourceforge.net] ], you should see: added dielectric function calculation for arbitrary q-vector, see 'LiF-Yambo' example (experimental) On Sat, 21 May 2016, ben amara imen wrote:

Hi, Using Wien2k , I have calculate the imaginary part of dielectric function (epsilon2) as function of photon energy. I have two questions: : 1) How I can know at which high point symmetry , the epsilon2 is calculated 2 ) I need to calculate , with wien2k, the imaginary part of dielectric function versus q ( epsilon 2=f(q)). How can I do this ? Thanks for your help

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