  Electronic, structural and thermodynamic properties of the equiatomic alloy
TiZr are calculated within the electron density functional theory and the
Debye-Gruneisen model. The calculated values of the lattice parameters a and
c/a agree well with the experimental data for the alpha, omega and beta phases.
The omega phase is shown to be stable at atmospheric pressure and low
temperatures; it remains energetically preferable up to T=600K. The alpha phase
of the TiZr alloy becomes stable in the range 600K<T<900K, and the beta phase
at temperatures above 900K. The constructed phase diagram qualitatively agrees
with the experimental data available. The tendency toward decomposition in the
equiatomic alloy omega-TiZr is studied. It is shown that in the ground state
the omega phase of the ordered equiatomic alloy TiZr has a tendency toward
ordering, rather than decomposition.
