I would like to calculate the dielectric function in the EUV region (photon energy = 92 eV) for a cluster-type material using VASP. When I added the LOPTICS tag in the INCAR file and performed the calculation, the dielectric function was only computed up to around 30 eV, and I am not getting results for higher energy ranges. I am wondering how I can modify my calculation to obtain the dielectric function in the 92 eV region. Since this is my first time calculating the dielectric function, I would greatly appreciate any assistance you could provide. Thank you in advance!
Hey Woongpyo Jeon
You might wanna try increasing the NBANDS in the INCAR file to include more conduction bands, so you can capture transitions at higher photon energies, like 92 eV. Also, increase the number of points in the energy grid with the NEDOS tag (larger NEDOS gives finer energy resolution). If you’re using hybrid functionals like HSE or PBE0, tweak the ENCUTFOCK tag. If not, consider switching to them. They might help!
Best,
Gabriel Vinicius
Gabriel Vinicius
Thank you for your excellent response. It was very helpful. As per your advice, increasing the NBANDS value allowed me to obtain results for the dielectric function at higher energy levels. Although I did not use a hybrid functional in my previous calculations, I will consider using one as you suggested. However, I have one question: is the reason you recommend using a hybrid functional because it is more suitable for dealing with calculations at high energy regions (~92 eV)?
Thank you in advance.
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