Dielectric properties

[IBRAHIM]

Dear All,

I am calculating the optical properties using VASP for 2D systems.

Using optics.sh script, I got IMAG and REAL files (attached).

My question is: I found another block of data in IMAG and REAl files after dim="1">gridpoints</dimension>. What does it mean? Should be considered during plotting the optical properties?


Many thanks in advance,
Ibrahim

[ferenc_karsai]

Please specify more precisely where your optics.sh is from. We don't provide any supported scripts like this. It looks like it is from a tutorial example, but then we highly discourage the users to take this scripts for other purposes than the specified example, since they are specifically written for a given example without any attempt to make them generally work.

[IBRAHIM]

Thanks for your reply.

I used the script (attached) from vaspkit to deal with the 2D systems.

Also, I used P4VASP to visualize the real and imaginary parts and did not show that block of data.

Best regards,
Ibrahim

[ferenc_karsai]

We have no connection to implementation of the Vaspkit, so we cannot give support to that.

Nevertheless concerning your problem, there are two types of dielectric functions printed out in VASP:
Density-density and current-current. Both start with IMAG and REAL, and your script only greps for these keywords.
So both dielectric functions are printed out and that should explain the extra columns.

[IBRAHIM]

Thank you very much for your explanation.

I see that in old VASP version 5.4.1, it was only written as for example: frequency dependent IMAGINARY (REAL) DIELECTRIC FUNCTION (independent particle, no local field effects) in OUTCAR.

But from VASP 5.4.4, the columns as you explained: frequency dependent IMAGINARY (REAL) DIELECTRIC FUNCTION (independent particle, no local field effects) density-density and frequency dependent IMAGINARY (REAL) DIELECTRIC FUNCTION (independent particle, no local field effects) current-current (2nd set in vasprun.xml).

So which part should be considered? because on vaspwiki, it was the old version and there is no explanation for that. And hopefully that can be modified on vaspwiki.

Best regards,
Ibrahim

[ferenc_karsai]

In my experience the density-density matrix is more often used in literature. But in most cases they are similar/equivalent.

[IBRAHIM]

Thank you.