Local atomic motions which were associated with phonon anomalies and point defects were studied by using a molecular dynamics method to examine the role of crystal defects in displacive phase transformations. Semi-empirical interatomic potentials, including many-body terms, were included in a molecular dynamics simulation. The experimental phonon anomalies which were related to the present phase transformations were accurately reproduced. A system for calculating electron diffraction patterns and high-resolution electron micrographs was established. This was based upon using the resultant atomic positions, from the molecular dynamics simulations, to compare simulations and experimental results. Two types of ω-phase transformation in Zr and ß-NiAl were chosen as examples, and certain types of point defect were found to act as pinning centers of the atomic motions which could induce phase transformation. The atomic displacements and their relaxation times were enhanced around the defects. The results suggested that the point defects could function as nucleation sites for phase transformations, via spatial fluctuations in strain distributions.

Molecular Dynamics Study of Local Atomic Displacements Associated with Point Defects and Displacive Phase Transformations. S.Muto, Y.Masuda, M.Takeuchi: Materials Transactions, 1999, 40[6], 514-21