I am working on simulating XAS by DFT in VASP for a group of MoxSy-based chalcogels, including MoS2, MoS4 and Mo3S13. Based on experimental data I should see XAS peak at around just above 20000 eV for K-edge of Mo; however when the SCH calculation is done, I just get the zero values for IMAGINARY part of the dielectric function in the OUTCAR file. I believe the code works fine, because when I caluclate the L-edges for Mo, I can see the absorption values for those within the expected electron binding energy ranges, however VASP outputs the dielectric function in fortran format 12F6. I think what's happening here is that for K-edge the dielectric function is too small such that the leading decimals are all zero. Dielectric function of material will be vanishingly small as the energy increases which should be obvious as it would be harder to excite core electrons and the deeper the more challenging it is. It should scale as 1/energy^2.

Thank you,

Here is my INCAR:

ALGO = Normal

CH_LSPEC = True

CH_NEDOS = 10000

CH_SIGMA = 0.05

CLL = 0

CLN = 1

CLNT = 1

CLZ = 1.0

EDIFF = 1e-05

EDIFFG = -0.01

ENCUT = 400

ICORELEVEL = 2

ISMEAR = 0

ISPIN = 2

LCHARG = False

LORBIT = 11

LREAL = Auto

LWAVE = False

NBANDS = 200

NCORE = 4

PREC = Accurate

SIGMA = 0.05

SYMPREC = 1e-05

NSIM = 16

KPAR = 1