Cluster approach to the Ti₂Ni structure type

Abstract

It has been established that the 16(c) first coordination clusters in the Ti2Ni structure type (space group Fd3m) follow icosahedral-face orientational ordering along regular tetrahedron edge directions. The actual crystal structure appears due to the prevalence of the face-centred cubic translational ordering over the cluster assembling. This way, the competition of the ;regular' crystal phase and its icosahedral analogue is reconstructed at the atomic level. The model accounts for the markedly different electronic characteristics at the different crystallographic positions obtained by hyperfine interaction measurements, and other curious experimental facts help to create an exact physical definition of the first coordination in the solid state and to distinguish between various structure types on fundamental principles.

Predicting whether a material is ductile or brittle

“…crystal lattice (space group Fd3m) with 96 atoms in the unit cell and, for the case of titanium and nickel, a lattice parameter of 11.28Å [75,76]. The range of elements that can be incorporated into the structure is also large, a search using the Inorganic Crystal Structure Database (ICSD) [77] While in many phases, the conceptualisation of structure as clusters are simply a geometrical description [78], in the Ti 2 Ni phases there is direct evidence that the bonding and properties are highly localised into the clusters, particularly around the 16(c) titanium site [79]. Ivanović, Rodić, Koteski et al [79] report the electric field gradient of the material to be extremely heterogeneous, showing different bonding at the two titanium sites, the 16(c) and the 48(f), just 3Å apart.…”

Microstructure and Tribological Properties of Lubricating-Reinforcing Laser Cladding Composite Coating with the Ti2SC-Ti2Ni Mosaic Structure Phase

“…As the intermetallic compound, Ti 2 Ni is a typical coating reinforcing phase with high microhardness and a complex face-centered cubic (FCC) structure [29]. According to the Ti-Ni binary alloy phase diagram, TiNi can produce Ti 2 Ni in a Ti-rich environment [30].…”

“…Moreover, when the lattice misfit is lower, the consumed twophase mismatch energy is lower and more atoms are matched on the two-phase mismatch interface, which leads to the stronger binding force of the two phases in the composite structure phase [31]. Due to the fact that the melting point of Ti 2 SC is higher than that of Ti 2 Ni [29], Ti 2 SC would precipitate before Ti 2 Ni. Therefore, for the Ti 2 SC-Ti 2 Ni mosaic structure composite phase, Ti 2 SC was the substrate phase and Ti 2 Ni was the nucleation phase.…”

Electronic Principles of Hydrogen Incorporation and Dynamics in Metal Hydrides

“…The established fact that some local structures inside the very same unit cell of the complex compounds of the Ti 2 Ni structure type are much more susceptible to H absorption than others [104,105], should be due to remarkably different charge topology observed at different lattice positions in some of these systems [106].…”