optical properties using random phase approximation Method

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abdul_jaleel1
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optical properties using random phase approximation Method

#1 Post by abdul_jaleel1 » Sat Apr 24, 2021 7:47 pm

Dear Users
I want to calculate optical properties using RPA method. In IPA calculations, the OUTCAR file contains frequency dependent function. But while coping with WAVECAR and WAVEDAR file from IPA calculations I have tried to calculate RPA based optical properties but I have observed zero values in real and imag part of dielectric functions.
ICAR for IPA Calculations:
ALGO = Exact
NBANDS = 64
LOPTICS = .TRUE.
CSHIFT = 0.100
NEDOS = 2000
ISMEAR = 0
SIGMA = 0.01
EDIFF = 1.E-8
NGX = 80
NGY = 48
NGZ =384
while for RPA calculation after coping WAVECAR and WAVEDAR file from IPA folder
ALGO = CHI
NBANDS = 64 (Take the same number of bands in the previous step)
ISMEAR = 0
SIGMA = 0.01
EDIFF = 1.E-8
LWAVE = .FALSE.
LCHARG = .FALSE.
! LRPA = .FALSE. (Set .FALAE. to include contributions from DFT exchange and correlation)

OUTCAR file is attached.
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ferenc_karsai
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Re: optical properties using random phase approximation Method

#2 Post by ferenc_karsai » Mon Apr 26, 2021 9:24 am

Please upload all the neccessary files according to the forum guidelines, so that we can better analyze your calculations.

abdul_jaleel1
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Re: optical properties using random phase approximation Method

#3 Post by abdul_jaleel1 » Mon Apr 26, 2021 9:51 am

Files are attached.
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ferenc_karsai
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Re: optical properties using random phase approximation Method

#4 Post by ferenc_karsai » Thu May 06, 2021 5:52 am

I reran your calculation using VASP.6.2 and got an error in the ALGO=CHI step with your setup.
Then I tried using a gamma centered KPOINTS file and the calculation worked properly (although I used a reduced k mesh).

So please try using a gamma centered KPOINTS file.
Also do the calculation in three steps:
First ALGO=NORMAL
Second ALGO=EXACT (with ISTART=1).
Third ALGO=CHI.

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