optical spectrum

[MB]

I am trying to calculate the value of dielectric constant for black phosphorous as per the publication
However the values are not matching with that of the reported ones. (along c=12.5, along a=10.2 and along b=8.3). 
Though the dielectric constant value along c axis is more or less close to that reported in the paper the values along other two directions are far apart. Change in the the 'k grid points' and the 'bands above and below Fermi level' were done, still there was no match.
Please help.

[kstokbro]

not sure what you are comparing with. Note that DFT-LDA gives wrong band gap which affects the calculation of the dielectric constant. Try using the Mgga

[MB]

I have been doing the simulations using mgga only.... .