  A procedure is presented that combines density functional theory computations
of bulk semiconductor alloys with the semiconductor Bloch equations, in order
to achieve an ab initio based prediction of the optical properties of
semiconductor alloy heterostructures. The parameters of an eight-band
kp-Hamiltonian are fitted to the effective band structure of an appropriate
alloy. The envelope function approach is applied to model the quantum well
using the kp-wave functions and eigenvalues as starting point for calculating
the optical properties of the heterostructure. It is shown that Luttinger
parameters derived from band structures computed with the TB09 density
functional reproduce extrapolated values. The procedure is illustrated by
computing the absorption spectra for a (AlGa)As/Ga(AsP)/(AlGa)As quantum well
system with varying phosphide content in the active layer.
