Dorian M. Hatch

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We propose a new direct mechanism for the pressure driven ! ! martensitic transformation in pure titanium. A systematic algorithm enumerates all possible pathways whose energy barriers are evaluated. A new, homogeneous pathway emerges with a barrier at least 4 times lower than other pathways. The pathway is shown to be favorable in any nucleation model.(More)
We have theoretically investigated the mechanism of the pressure-induced reconstructive zinc-blende to rocksalt phase transition in SiC. We obtained 925 possible transition pathways ͑TPs͒ using a group-theoretical analysis method. This extensive survey of possible TPs is a significant feature which distinguishes this study from previous studies. Of these(More)
Martensitic phase transitions appear in a diverse range of natural and engineering material systems. Examination of the energetics and kinetics of the transformation requires an understanding of the atomic mechanism for the transformation. A systematic pathway generation and sorting algorithm is presented and applied to the problem of the titanium ␣ to ␻(More)
Three possible mechanisms for the reconstructive phase transition from the B1 to the B2 structure types are examined: ͑1͒ a modified Buerger ͑MB͒ pathway, ͑2͒ the Watanabe ͑W͒ pathway, and ͑3͒ a new pathway ͑T͒ proposed by Tolédano et al. ͓Phys. Rev. B 67, 144106 ͑2003͔͒. We use first-principles energy calculations to obtain barrier heights for these(More)
A variety of structural transitions in nature do not involve a group-subgroup relationship. A two-dimensional example is the transition between a square lattice and a triangular lattice, which is known to occur in vortex lattices, Wigner crystals, skyrmion lattices, colloids, diblock copolymers, etc. A three-dimensional analog is the shock-induced BCC to(More)
We have classified continuous phase transitions in physical systems where the order parameter transforms as a six-dimensional representation of a space group. The Landau potential is minimized with the use of Kim's geometrical method and a table of isotropy subgroups recently obtained by Stokes and Hatch. For most images of the active six-dimensional(More)
A comparison is made of two different approaches to the description of phase transitions in the A2BX4 structure (space group D4&, I4/mmm) due to rigid octahedral tiltings. The lower-symmetry subgroups due to coupling of the K»f (X2) and E&2~ (P4) representations (6 tilts) to other tilting modes are listed. All observed transitions in the A2BX4 structure are(More)
Two tables are presented which result from the symmetry analysis of the microstructure, i.e. , atomic site locations, for a system with space-group symmetry R 3c (D 3d). The first table contains information about transition order parameters. Representations, allowed subgroup symmetries, Landau and Lifshitz frequencies, changes in primitive-cell size,(More)