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### ElecTemp in RPA dielectric function

Posted: **Tue Feb 19, 2019 1:58 pm**

by **Weiqing Zhou**

Hi all,

I calculated optical response of a metal material and use RPA with local field effect to obtain dielectric function. I find the result would change a lot if I set different ElecTemp. I don't understand why the imaginary static dielectric function ( imaginary dielectric function at /Omega=0 ) is not zero when I set ElecTemp = 0.0 eV.

You can check the output with 0K and 300K in attachment.

Best,

Weiqing

### Re: ElecTemp in RPA dielectric function

Posted: **Wed Feb 20, 2019 9:53 am**

by **Daniele Varsano**

Dear Wiking,

this is probably becuase your temperature it is not exactly zero.

From the report you can see:

Code: Select all

`[X]Electronic Temp. [ev K]: 0.8617E-5 0.1000`

and this happens as the system is metallic.

Anyway the values you get at omega=0 it is also affected by the smearing you used:

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```
% DmRngeXd
| 0.10000 | 0.10000 | eV # [Xd] Damping range
| %
```

you can think to low that value.

Note also that, to have a correct description of the metallic behavior it would be appropriate to add the Drude term in your response function:

Code: Select all

` [WARNING] The system is a metal but Drude term not included.`

Best,

Daniele

### Re: ElecTemp in RPA dielectric function

Posted: **Wed Mar 13, 2019 1:37 pm**

by **Weiqing Zhou**

Dear Daniele,

Thanks for you kind reply!

I add Drude term into dielectric function (by DrudeWXd). For q1 (0,0,0), I find that there appears a very large value around /omega=0 in dielectric function. But for finite q, Drude term makes no difference in dielectric function. Is it right?

Best,

Weiqing

### Re: ElecTemp in RPA dielectric function

Posted: **Wed Mar 13, 2019 1:41 pm**

by **Daniele Varsano**

Dear Weiqing,

indeed, the Drude term takes into account the term coming for interband transitions in the limit q->0.

For finite q, interband transitions are correctly taken into account in the response function

Best,

Daniele