  Thin films of CdTe were deposited on glass substrates by thermal evaporation.
  From the XRD measurements itis found that the films are of zinc-blende-type
structure. Transmittance, absorption, extinction, and refractive coefficients
are measured. Electronic structure, band parameters and optical spectra of CdTe
were calculated from ab initio studies within the LDA and LDA+U approximations.
It is shown that LDA underestimates the band gap, energy levels of the Cd-4d
states, s-d coupling and band dispersion. However, it calculates the spin-orbit
coupling correctly. LDA+U did not increase much the band gap value, but it
corrected the s-d coupling by shifting the Cd-4d levels towards the
experimentally determined location and by splitting the LDA-derived single s
peak into two peaks, which originates from admixture of s and d states. It is
shown that the sd coupling plays an important role in absorption and
reflectivity constants. The calculated optical spectra fairly agree with
experimental data. Independent of wave-vector scissors operator is found to be
a good first approximation to shift rigidly the band gap of CdTe underestimated
by LDA.
