My Community

To whom it may concern,

We want to calculate electron energy loss spectra (EELS) along a specific path (e.g. G-M-K) using VASP. The EELS requires the q-dependant dielectric function which according to this VASP wiki page (https://www.vasp.at/wiki/index.php/Cate ... properties) can be calculated using the ALGO = CHI or ALGO = BSE methods. I have a few of questions about obtaining EELS from VASP:

1. I ran the tutorial calculation for SiC from the wiki (https://www.vasp.at/wiki/index.php/Diel ... ies_of_SiC), see attached SiC_tutorial.zip folder, and it only prints the dielectric function for q = 1 (see OUTCAR.CHI), all other q-points indicate they are calculated but are not output.
Is it possible to output the dielectric function for all q-points using ALGO = CHI?

2. I also came across the new KPOINT_BSE tag which allows for calculation of the dielectric function using the BSE method at a specific q-point.
Can KPOINT_BSE or any other tag/method take a list of q-points and calculate the dielectric function? or would we have to use a script to calculate our dielectric functions for the list of q-points along our path?
Also, is it possible to use KPOINT_BSE with ALGO = CHI?

Kind regards,
Oliver

I believe KPOINTS_BSE is the way to go. Consider this subsection for an example input file. As far as I can tell, the output is only written to xml/hdf5 and not to OUTCAR.

I will inquire to get more information about this particular technique and see which methods it should be compatible with.

Many thanks!

Kind regards,
Oliver

Dear Martin,

Just following up if you've had a chance to inquire about which methods this technique can be applied?

Kind regards,
Oliver

Thank you for the reminder. I did get the feedback that at this stage BSE and TDHF are the only way to get finite q dielectric functions. As mentioned above, you use KPOINTS_BSE to do that.