  Ab-initio calculations for the structural properties of Zr-Nb alloys at
different values of the niobium concentration are done at zero temperature.
Different cases for Zr-Nb alloys with unit cells having BCC and HCP structures
are considered. Optimal values of the lattice constants are obtained. Critical
value for the niobium concentration corresponding to the structural
transformation HCP \rightarrow BCC at zero temperature is determined.
Electronic densities of states for two different structures with niobium
concentrations 12.5% and 25% having HCP and BCC structures, accordingly, are
studied.
