keyword issues

[manaswitakar]

Hi,

I am trying to calculate the quasiparticle band gap of MAPbI3 using yambo. In principle, I am trying to reproduce the results by Filip and Giustiono (PRB 90, 245145, 2014). There, they mention to use exchange self-energy cutoff of 408 eV and correlation self-energy cutoff of 82 eV. They further mention to use a polarisabilty cutoff of 82 eV.

My question is: 1. How to setup these parameters in yambo input file?
2. To my understanding, yambo only accepts RL units. So, I need to convert the ev to RL every time?
3. Which keyword corresponds to polarisability cutoff?
4. The exchange self energy is EXXRLvcs and correlation self energy is VXXRLvcs?
5. Do I need to change the kinetic energy cutoff in DFT calculations as well?

Thanks and Regards,
Manaswita

[Daniele Varsano]

Dear Manaswita,
please add your affiliation in your signature, you can do once for all by filling the signature in your user profile.

2. To my understanding, yambo only accepts RL units. So, I need to convert the eV to RL every time?

Yambo accepts also Ha, Ry and its submultiples mHa, mRy.

3. Which keyword corresponds to polarisability cutoff?

This is the dimension of the dielectric matrix (NGsBlkXp) in plasmon pole approximation.

The exchange self energy is EXXRLvcs and correlation self energy is VXXRLvcs?

EXXRLvcs is the exchange self energy, while the correlation self-energy is the same of the polarisability cutoff. VXXRLvcs controls the FFT grid to evaluate the exchange-correlation potential to be subtracted to the self energy, and I would leave to its maximum when possible.

5. Do I need to change the kinetic energy cutoff in DFT calculations as well?

No, once the DFT calculation is well converged you can stay with that, it fix the maximum G vectors you can sue in all the other parameters.

Best,

Daniele