PHONON LOCALIZATION AND MARTENSITIC-TRANSFORMATION IN NIXAL1-X ALLOYS

With the embedded-atom method we determine the normal vibrational modes of NixAl1-x, which displays a martensitic transformation (MT) for 0.61 less-than-or-equal-to x less-than-or-equal-to 0.66. In the high-temperature phase the compositional disorder induces several bands of localized phonons that discontinuously delocalize at the MT. The analysis of the phonon eigenvectors allows one to identify the atomic arrangements inducing localization. We show that the modes associated with Ni-rich clusters can be used to monitor incipient lattice instabilities, and identify regions with low barriers for nucleation of the martensite.