Ab Initio Investigations of Phonon Anomalies and Martensitic Transformations

AB INITIO INVESTIGATIONS OF PHONON ANOMALIES AND MARTENSITIC TRANSFORMATIONS 

Heike C. Herper, Egbert Hoffmann, and Peter Entel 

Theoretische Tieftemperaturphysik, Gerhard-Mercator-Universitat GH, Lotharstrafie 1, 

Martensitic phase transformations are discussed for the last hundred years without loss of actuality. A concise definition of these structural phase transformations has been given by G.B. Olson stating that martensite is a diffusionless, lattice distortive, shear dominant transformation by nucleation and growth . In this work we present ab initio zero temperature calculations for two model systems, FeaNi and CuZn close in concentration to the martensitic region. Iron-nickel is a typical representative of the ferrous alloys with fee bet transition whereas the copper-zink alloy undergoes a transformation from the open to close packed structure.  

Lattice vibrations are calculated by applying the second order perturbation theory approach of Varma and Weber , thereby combining first principles short range force constants with the electron-phonon coupling matrix arising from a tight-binding theory. 

---