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[Bohdan Andriyevskyy <bandri@tu.koszalin.pl>]

Dear Giovanni,
I would like to say that I have also encountered this problem, and also 
in other versions of abinit. I could not obtain realistic results using 
the optic program for other crystals.

Regards,
Bohdan

giovanni.cantele@na.infn.it napisał(a):

> Dear all,
> I was trying to use the optic (4.6.4) program to calculate
> linear dielectric functions for some systems.
>
> As a check, I'm studying bulk Si, but I cannot obtain
> results consistent with the literature.
> I've tried to get convergence with respect to the cutoff and/or
> k-point mesh, with no success. For example, the transition at Gamma
> point is never present in the epsilon2.
>
> Nevertheless, looking at the sources, it seems that
> a problem in the module (or in the way I use it!) is present.
> In fact, the log file of the optic run always prints, in my case,
> fermie            =   0.00000 Ha   0.00000 eV
> Then, I tried to set the Fermi energy by hand in the optic.F90,
> obtaining results which are similar to those found in the literature.
>
> So, the question is: is there a problem in the reading of the Fermi
> energy in the optic program or this problem could be due to wrong settings
> in some of the input files?
>
> One more question: the output of optic contains lines like
>
> # Energy(eV)         Im(chi1(w))
> #calculated the component:  1  1of linear susceptibility
>
> Just to be sure: does the output actually contain the dielectric function
> espilon?
> Within linopt I found
>
> eps(iw)=1.d0+4.d0*pi*chi(iw)
> ...
> write(92, '(2es16.6)' ) ene,aimag(eps(iw))
>
>
> Thanks for help
> Giovanni
>
>
>