How to set NBANDSV and NBANDSO

[Jike.Wang]

Dear all,

I am doing some excitonic calculations using TDHF, and there are two parameters should be set, which are NBANDSV and NBANDSO. But I am not very clear that how to set them for different materials. How large values are recommended? Could you give me some advice?

Thanks.

[merzuk.kaltak]

Dear Jike Wang,

Thank you for your question regarding NBANDSV and NBANDSO parameters in TDHF excitonic calculations.
The optimal values depend on your accuracy requirements:

Qualitative results
The default VASP settings generally suffice, providing reasonable approximations without excessive computational costs.

High-accuracy results
Systematically increase both parameters while monitoring:

• Convergence of excitation energies

• Occupation of highest included bands

• Computational resource constraints

Convergence testing remains essential as no universal values exist across materials systems. For critical applications, consider pushing these parameters to your hardware's memory/storage limits while verifying result stability.