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Hi,

I have the optical transitions from the vasprun.xml file for a BSE/TDHF calculation. However, in addition to the energies of each transition I'm interested in knowing the bands/orbitals involved in that specific transition (i.e. from which band to which band does the transition correspond to). I can't seem to find the corresponding information in the output files...could you please help me with this? Alternatively, if there are suggestions for any post-processing software that can do this that would be awesome as well

thanks!

Hi awang95,

You can find this information, i.e. the contribution of the individual transitions into the excitonic state, in the BSEFATBAND file.

thanks!

should the highlighted part of this picture from the wiki be NB_e?

sorry I would like to clarify another thing

from the BSEFATBAND output it seems that the values correspond to the below as noted (it only makes sense if I interpret it this way), which is different from the order posted on the wiki - can I confirm whether if the below would be correct? thanks

It's a typo, thanks for pointing that out. Actually, these are the valence and conduction band energies and numbers, so I changed the notation on the wiki accordingly. Does that answer your question?

yes thanks!

sorry just like to follow up on this as I'm now interested in the eigenvectors: I'm not quite sure what it means when the wiki says "X_BSE" corresponds to the "component of the eigenvector" - is it the component in the x-direction only or something else? I think I'm not really sure which eigenvector and what component of it the "X_BSE" is referring to here. Also, what physical information can we extract from Abs(X_BSE) and Re(X_BSE)+i*(X_BSE)? sorry if this is too obvious or stupid - I'm still quite new to this and have been quite confused for a while

thanks!

The BSEFATBAND file stores the eigenvectors of the BSE Hamiltonian found when we diagonalize the Hamiltonian. X_BSE are the components of the these eigenvectors which are essentially the coupling coefficients or contributions of individual transitions between valence and conduction bands. Using this information you can make a fatband plot as described on the wiki Plot BSE fatbands. Such a plot can give you an idea of what transitions contribute the most to an excitonic state and how localized this state is.

ok thanks so much!