Alpha to omega martensitic phase transformation pathways in pure Zr

• Published in: Journal of alloys and compounds 2014-02, Vol.586, p.693-698
• Main Authors: Ghosh, Partha S., Arya, A., Tewari, R., Dey, G.K.
• Format: Article
• Language: English
• Subjects: Band structure of solids; Barriers; Computer simulations; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Elasticity, elastic constants; Electronic band structure; Enthalpy; Exact sciences and technology; High pressure; Lattice dynamics; Martensitic transformations; Materials science; Mathematical models; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Pathways; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Phase transitions; Phonon states and bands, normal modes, and phonon dispersion; Phonons; Phonons and vibrations in crystal lattices; Physics; Symmetry; Transformations
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.10.045

•This Ab-initio study determines lowest enthalpy barrier TP for α→ω in Zr.•Most favorable TP has a C2/c common sp. gr. and 22meV/atom enthalpy barrier at 0K.•This TP comprises of small strains and atomic shuffles compared to other TP.•Softening of C44 and ωE2g associated with change in E2g phonon mode potential landscape.•E2g phonon mode and pressure shows a similar topological change in band structure. This first principles study attempts to find the lowest enthalpy barrier transformation pathway (TP) for pressure induced α→ω transformation in pure Zr by systematically studying TPs suggested experimentally along with TPs generated from symmetry analysis. We find that symmetry generated pathways and model pathways given from experimental inputs essentially outline the same subset of possible pathways. The most favorable TP, comprising of smaller strains and atomic shuffles compared to others, has a C2/c as a common space group along the TP with enthalpy barrier of 22meV/atom at 0K. It is evident from the study that the softening of shear elastic constant C44 and Γ point transverse optical phonon frequency as a function of pressure in α-Zr are associated with change in effective potential landscape for the E2g phonon at Γ point of the Brillouin zone. The calculated electronic band structure as a function of pressure and E2g phonon mode shows a similar topological change in the band structure which drives this transformation.