Anharmonic model of instability evolution near the bcc→hcp phase transition in Zr

A local minimum is observed on the full-potential linear-muffin-tin-orbital curve of total energy versus the amplitude of atomic displacements corresponding to transverse [1 (1) over bar 0] vibrations at the N paint of the Brillouin zone in Zr. The temperature dependence of the inelastic one-phonon neutron-scattering spectra is calculated within the framework of a modified pseudoharmonic approximation. The appearance of the spectrum fine structure with decreasing temperature is associated with the intermediate phase phonon whose frequency is close to that of the a phonon of hcp Zr.