Abstract
Abstract Ti3Sb and Ti3Ir adopt the A15 (Cr3Si type) structure and are reported to incorporate hydrogen atoms to an extent, respectively, of Ti3SbH∼3 and Ti3IrH3.8. First-principles electronic structure calculations were performed to identify factors contributing to the difference in maximum hydrogen composition for these two intermetallic compounds. Relative energies and changes in energy densities of states and crystal orbital Hamilton populations upon H insertion in the intermetallic compounds were examined. In both compounds, hydrogen atoms are attracted to [Ti4] tetrahedral interstitial sites over any others. The natures of metal-hydrogen and metalloid-hydrogen bonding and the effects of hydrogen insertion on metal-metal and metal-metalloid bonding have an influence on the maximum hydrogen contents for Ti3Sb and Ti3Ir.
Highlights
The absorption of hydrogen in metals and intermetallics has interested chemists, physicists, materials scientists, and material engineers over many decades for fundamental and applied scientific reasons
Firstprinciples electronic structure calculations were performed to identify factors contributing to the difference in maximum hydrogen composition for these two intermetallic compounds
Hydrogen uptake in intermetallic compounds may cause a change of crystal structure [1, 2], which can lead to embrittlement or to significant changes in the physical properties [3, 4]
Summary
The absorption of hydrogen in metals and intermetallics has interested chemists, physicists, materials scientists, and material engineers over many decades for fundamental and applied scientific reasons. Many of them absorb considerable amounts of hydrogen without changing structure and exhibit a linear expansion of the lattice parameter as the hydrogen concentration increases. Of these compounds, only a few have been examined by neutron diffraction to locate the hydrogen or deuterium atoms, such as Nb3SnHn [13], Ti3SbDn [14] and Ti3IrDn [15]. Superconductivity is eliminated generally before the maximum hydrogen composition is reached, e.g., in Ti3SbHn no superconductivity is observed for n ≥ 1 [19]. This communication attempts to elucidate factors in the electronic structures of Ti3SbHn and Ti3IrHn (n ≥ 0) that contribute to their maximum hydrogen compositions and site preferences
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