  The band structure of (ZnxCd1-x)3P2 alloy system is considered within the
framework of Kildal's band model. Frequency dependencies of real and imaginary
parts of dielectric function were received and analyzed in terms of direct band
to band transitions. Theoretical calculations were performed for light
polarized both parallel and perpendicular to the c- axis of the crystal. In
calculations the selection rules for optical transitions were applied. The
frequency dependence of real part of dielectric function is described by a
maximum in hv=(1,2 - 1,5)Eg energy region. In high energy region hv>>Eg the
imaginary part of dielectric function has a plateau. Longitudinal dielectric
function is less than the transverse dielectric function for all compositions x
of (ZnxCd1-x)3P2 alloy system both for real and imaginary parts. When turning
from Zn3P2 to Cd3P2 the reduction of dielectric function values occurs.
