  Ab initio studies of structural, elastic and electronic properties of the
tetragonal perovskite-type PbZr0.5Ti0.5O3 are presented using the
pseudo-potential plane wave method within the density functional theory in
generalized gradient approximation. The calculated equilibrium lattice
parameters remain in a good agreement with the available experimental data. The
bulk modulus obtained from the Birch-Murnaghan equation of state is calculated
as B0=170 GPa, and the gap energy Eg=2.1 eV-3.5 eV. The some differences
between calculated and nominal charges exist for all atoms. The biggest ones
are on the Pb ions. They are caused by hybridization of the Pb 6s and O 2p
states. The influence of the strain on the averaged over directions Young
modulus in the 0.1%-0.3% range was studied.
