I started with structure Optimization and then ran SCF calculation to Generate WAVECAR file.
Then calculated Plasma frequency using LOPTICS=.TRUE. and following tags.
is the approach correct for calculating plasma frequency?
ISTART = 1
#ICHARG = 0
LOPTICS = .TRUE.
ENCUT=450
NELM = 100
EDIFF = 1.E-05
EDIFFG = -.02
NBANDS =24
Ionic Relaxation
NSW = 0
IBRION = 2
ISIF = 2
ISYM = 1
POTIM = .05
# DOS related values:
ISMEAR = 0
SIGMA = .1
NEDOS = 2000
Hybrid calculation
ALGO = Exact ;
# NKRED = 2
#GGA+U
LDAU = .TRUE.
LDAUTYPE = 2
LDAUL = -1 2 -1
LDAUU = 0.00 2.30 0.00
LDAUJ = 0.00 0.00 0.00
I do not think that 24 bands are enough to describe the excitations of realistic material. Especially since you are using a U Hubbard term to account for d or f shell electrons in your system which indicates that there are many electrons in your system. So my first suggestion would be to increase the number of bands to include enough 'virtual' bands. The other point I will mention is that you should also do a convergence test with respect to the k-mesh you use. Because the calculation of the imaginary part of the dielectric response is basically a summation over the points in your mesh in reciprocal space, the valence bands, and the conduction bands. See the exact relation here:
https://www.vasp.at/wiki/index.php/LOPTICS
Now to answer your question:
Including LOPTICS will typically output the real and imaginary dielectric tensor in your OUTCAR files in addition to the plasma frequency. However, depending on your system and how accurately its electronic structure has been calculated, the value for the plasma frequency will vary but you should be within reason. For your system, for example, you may want to see (if/how) changing the U parameter affects the calculated plasma frequency. However, If you are trying to match experimental values, you may have to use BSE or TD-HF. In that case, you may follow the following VASP tutorial.
https://www.vasp.at/wiki/index.php/Bethe-Salpeter-equations_calculations
I hope this answers your question
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