[Wien] Why dielectric function differs by 1 ?

[gbliu]

Dear Xavier,

Thank you very much for your hint. I have known that this originates
from KK raltion.

Best withes.

Liu Gui-Bin

于 2011/7/2 18:40, Rocquefelte 写道:
> Dear Liu,
>
> It is related to the Kramers-Kro"nig relation.
> Looking at these equations you will see that eps2 is an additive
> quantity, while for eps1 you should consider (eps1 - 1) ...
>
> Regards
>
> Xavier
>
>
>
> On 06/30/2011 07:47 PM, gbliu wrote:
>> Dear all,
>>
>> I calculated the dielectric function of fcc Au, using a k-mesh
>> 15x15x15. After the scf run, my step is as follow:
>> 1. x opitc
>> 2. Calculate intraband contribution, by setting swith 6 in
>> fccAu.injoint file. Then I run "x joint".
>> 3. Read the file fccAu.outputjoint, and get the plasma frequencies:
>> 9.0075eV for both xx and zz.
>> 4. Save a copy of fccAu.joint as *Intra.epsilon*, in which is the
>> data of dielectric function from intraband contribution (Drude model).
>> 5. Change the swith in fccAu.injoint from 6 to 4. "x joint" to
>> compute epsilon.
>> 6. "add intraband" set to 0 in fccAu.inkram, then "x kram", save the
>> file fccAu.epsilon as *noIntra.epsilon*
>> 7. "add intraband" set to 1 in fccAu.inkram, then "x kram" again,
>> save the file fccAu.epsilon as *withIntra.epsilon*.
>> 8. Then I compare the data in files Intra.epsilon, noIntra.epsilon
>> and withIntra.epsilon, I found that:
>> Im(withIntra.epsilon) = Im(noIntra.epsilon) + Im(Intra.epsilon)
>> But Re(withIntra.epsilon) = Re(noIntra.epsilon) + Re(Intra.epsilon) - 1
>>
>> So I'm confused why not "Re(withIntra.epsilon) = Re(noIntra.epsilon)
>> + Re(Intra.epsilon)" ?
>> How does the difference "1" come from?
>>
>> Can anyone help me ?
>>
>> Thanks in advance.
>>
>> ---------fccAu.inop-------
>> 99999 1 number of k-points, first k-point
>> -5.0 3.0 9999 Emin, Emax for matrix elements, NBvalMAX
>> 2 number of choices (columns in *outmat): 2: hex or tetrag. case
>> 1 Re xx
>> 3 Re zz
>> OFF ON/OFF writes MME to unit 4
>> --------------------------
>>
>> -------fccAu.injoint------
>> 1 9999 9999 : LOWER,UPPER and (optional) UPPER-VAL BANDINDEX
>> 0.0000 0.00100 1.0000 : EMIN DE EMAX FOR ENERGYGRID IN ryd
>> eV : output units eV / ryd / cm-1
>> *4 * *"first I use 6, then 4" * : SWITCH
>> 2 : NUMBER OF COLUMNS
>> 0.1 0.1 : BROADENING (FOR DRUDE MODEL - switch 6,7 - ONLY)
>> --------------------------
>>
>> -------fccAu.inkram---------
>> 0.1 Gamma: broadening of interband spectrum
>> 0.0 energy shift (scissors operator)
>> *1 "first I use 0, then 1" * add intraband contributions? yes/no: 1/0
>> 9.0075 9.0075 plasma frequencies (from joint, opt 6)
>> 0.10 0.10 Gammas for Drude terms
>> ------------------------------
>> -- 
>> Best regards!
>>
>>                  Liu Guibin
>>              Postdoctoral Fellow,
>>              Department of Physics,
>>              The University of Hong Kong
>>              
>>
>>
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>
>
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