Photon enery range in RPA

[gurudayal_behera]

Hii Sir,
Please let me know how to choose the photon energy range to calculate the dielectric response function using the RPA method. Using the IPA method, I found that the total number of photon energies is 2001 points as I set NEDOS = 2001. But with the same NEDOS values when I did the RPA, I got only 100 photon energy points generated. Can you please explain how to increase and choose the photon energy range and step size to set the number of photon energy in RPA calculations?

Thanks in advance.

Best
Gurudayal Behera
IIT Bombay

[alexey.tal]

Hi,

In the calculation of the RPA dielectric function, the frequencies grid is determined by the NOMEGA tag, which is 100 by default. The response function has to be calculated for every frequency which is quite computationally demanding. To optimize it, VASP uses a denser grid up to OMEGMAX and a sparser grid beyond that. A reasonable choice of NOMEGA is described on the wiki page, but generally it is a convergence parameter.

[gurudayal_behera]

Thank You for response.