[Wien] Why dielectric function differs by 1 ?

[gbliu]

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
             

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20110701/c1e52636/attachment.htm>