An unreasonable results of exciton wavefunction in reciprocal space

[Shixuan]

Dear all,

I have complete DFT calculation via Quantum Espresso (WS2 with a k-mesh of 30*30), and try to find the exciton states of WS2 by BSE, YAMBO. After I finished Static screening, BS kernel runlevel, and BS diagonalization calculation, I try to plot some excitonic wavefunction in reciprocal space, but only find some exciton states with weird symmetry, just like shown in Fig.1.

However, form a previous work (Supporting Information of "ACS Nano 2022, 16, 5, 7428–7437"), the exciton with lowest energy (1s state) of WS2 has a local spherical symmetry, just like shown in Fig. 2.

Here, I think that this calculation did not achieve the required precision, while I have no idea on how to improve the accuracy of my calculation. Could you please tell me if there any input parameters needed to be modified?

I'm looking forward to your kindly reply.

All the Best,
Shixuan

Department of PHY,
City University of Hong Kong,
Hong Kong SAR

[Shixuan]

Dear all

There are some extra input files attached here.

All the best.
Shixuan

Department of PHY,
City University of Hong Kong,
Hong Kong SAR

[Daniele Varsano]

Dear Shixuan,

could you please share the results of the ypp analysis, in particular the o.*weight* and o.sort* files, together with a report file ?
Also, can you explain how you computed the excitonic wavefunction in reciprocal space?

Best,
Daniele

[Shixuan]

Dear Shixuan,

could you please share the results of the ypp analysis, in particular the o.*weight* and o.sort* files, together with a report file ?
Also, can you explain how you computed the excitonic wavefunction in reciprocal space?

Best,
Daniele

Dear Daniele,

Thank you for your kindly help. The excitonic wavefunction in reciprocal space was calculated by the A-coefficient of excitons. A-coefficient is describe as:



I just plot the real part of A-coefficient as a function of k-points, which gives these figures shown in this topic.

Besides, o.*weight* (belong to the exciton was shown in Fig.1), o.sort* (by both energy and strength) was shown in attached files.

All the best,
Shixuan

Department of PHY,
City University of Hong Kong,
Hong Kong SAR.

[Daniele Varsano]

Dear Shixuan,

looking at your excitation energies and intensities, it seems that the spectrum you obtain is not in agreement with the one you indicated in the previous post (see figure).

spectrum.png

You should check your structure and convergence parameters, as it is possible you are looking to a different exciton.

About the exciton wavefuncion, you attached the amplitude file and not the weight so I cannot look at it.
By default, yambo plot the |A_cv|^2, I presume you read the A_cv from the database, as I can see negative value, but as you plotter the real part it is possible you have a phase problem,
you can try to plot the square modulus and see its shape.


Best,
Daniele