ARE MARTENSITIC PHASE TRANSITIONS IN PURE GROUP 3 AND 4 METALS DRIVEN BY LATTICE VIBRATIONS ?

Abstract

The phonon dispersion in the high temperature bcc phase of the group 3 and 4 metals Sc, La, Ti, Zr and Hf have been determined by inelastic neutron scattering. In these pure elements the lattice vibrations are characterized by a valley of low energy modes, which are extremely damped, i.e. lifetimes as short as one vibrational period are measured. It is shown that these low energy vibrations exhibit a particular temperature behavior and are directly related to the transformation into the low temperature hcp or fcc phase or into the hexagonal [MATH]-phase under increasing pressure.