Speaker
Description
Keywords: First-principles calculations, Density functional theory (DFT), Elastic properties, Phase stability, Density of states, Phonon dispersion and Shape memory
Abstract: Most Ti-based CsCl-type (Pm3m) compounds solidifies congruently to an ordered B2 phase of high symmetry at high temperature and transforms martensitically to lower symmetry phases upon cooling to room temperature. In this work, the phase stability, the mechanical and electronic properties of three CsCl-type intermetallic compounds TiTM (TM=Ni, Ru and Pd) were computed using density functional theory (DFT) based on first-principle technique are reported. The obtained lattice parameters are in good agreement with our experimental XRD results, which is a good indication that the computational parameters used in this work can be reliable to calculate other physical properties. Enthalpy of formations (ΔHF) and density of states (DOS), which are used to evaluate the thermodynamic stability of the compound, were calculated from the geometrically optimized crystal structures. A high negative heats of formation (-0.75 eV/atom) was obtained for TiRu phase, and its Fermi level found to coincide with the center of the pseudogap demonstrating the high stability and resistance to phase transition amongst the three investigated compounds. The primary elastic constants (C11, C12 and C44) and shear elastic coefficient (C') for cubic crystals were calculated. It was found that TiRu showed mechanically stability while TiPd and TiNi were not mechanically stable. Furthermore, the TiRu was found to exhibit only positive frequencies, while TiPd and TiNi exhibit both positive and negative frequencies signifying possible phase transition to low symmetry phases such as L10/B19/B19' at lower temperatures, in agreement with experimental data.
Level for award;(Hons, MSc, PhD, N/A)?
MSc
| Apply to be considered for a student ; award (Yes / No)? | Yes |
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