Optical properties without LOPTICS tag

Question

I have performed some calculations for a 2D-monolayer using VASP. I run DOS calculations without LOPTICS = .TRUE. I found that when I run the vaspkit, I got the files for optical properties. Could someone please explain to me, if we are getting the files for optical properties, then how reliable are these files?

INCAR

ISTART   = 1
# ICHARG   = 11
# ISYM = 0
 PREC     = Accurate
 ENCUT    = 550
 ISMEAR   = 0
 SIGMA    = 0.1
 LREAL    = .FALSE.
 LWAVE    = .TRUE.  
 LCHARG   = .TRUE.   
 ADDGRID  = .TRUE.  
 EDIFF   = 1e-6
 EDIFFG  = -0.02
 NSW     = 0
  LORBIT  = 12
  NEDOS   = 5000
  LHFCALC= T
  AEXX   =  0.25 HFSCREEN= 0.2  
  ALGO   =  ALL
  TIME   =  0.4

Answer 1

• When you open the LHFCALC tag, the DFT hybrid functional type dielectric function is calculated. All the output files you obtain are calculated by VASPKIT using this dielectric function.

• https://vaspkit.com/tutorials.html#optic-properties

Could someone please explain to me, if we are getting the files for optical properties, then how reliable are these files?

• For 2D materials, these results cannot be believed. You should use the GW+BSE method to obtain reliable results. See this post for more information: How to start with the optical properties of 2D materials with the VASP code?