Inducing Complexity in Intermetallics through Electron–Hole Matching: The Structure of Fe₁₄Pd₁₇Al₆₉

Abstract

We illustrate how the crystal structure of Fe Pd Al provides an example of an electron-hole matching approach to inducing frustration in intermetallic systems. Its structure contains a framework based on IrAl , a binary compound that closely adheres to the 18-n rule. Upon substituting the Ir with a mixture of Fe and Pd, a competition arises between maintaining the overall ideal electron concentration and accommodating the different structural preferences of the two elements. A 2×2×2 supercell results, with Pd- and Fe-rich regions emerging. Just as in the original IrAl phase, the electronic structure of Fe Pd Al exhibits a pseudogap at the Fermi energy arising from an 18-n bonding scheme. The electron-hole matching approach's ability to combine structural complexity with electronic pseudogaps offers an avenue to new phonon glass-electron crystal materials.

The Zintl Concept Applied to Intergrowth Structures: Electron‐Hole Matching, Stacking Preferences, and Chemical Pressures in Pd5InAs

“…The AuCu 3 -type PdIn 3 and PtHg 2 -Pd 2 As structures are electron-poor and electron-rich, respectively, relative to pseudogaps corresponding to closed shell configurations. The intergrowth provides the opportunity for electron-transfer across the interfaces to cancel these effects, following the electron-hole matching mechanism [31] proposed previously for the stability of such arrangements.…”

“…This hints that the electron deficiency and excess in the parent structures have cancelled each other out, much like the recombination of electrons and holes in semiconductors as envisioned by the electron-hole matching mechanism for intergrowth stability. [31] The raMO schemes for the binary phases would then be expected to largely transfer to the ternary compound. Indeed, a sequence of raMO reconstructions of the As 4s and 4p orbitals, as well as the In 5s orbitals can be carried out without issues (Figure 5), yielding formal charges of As 3À and In + .…”

Optimization of Chemical Bonding through Defect Formation and Ordering─The Case of Mg7Pt4Ge4

“…Intense research activities on polar intermetallic compounds (PICs) are motivated by their rich structural chemistry and outstanding physical properties, like superconductivity, thermoelectricity, and magnetocaloric effects. − Some materials belonging to this class have become vital for innovative technologies such as renewable energy generation and storage or catalysis. − …”

Structure of Cubic Al73.8Pd13.6Fe12.6 Phase with High Al Content

“…Both the quasicrystals and their approximants in the Al-Pd-Fe alloys have been the subject of extensive research for their similarity and diversity of phases with those in the Al-Cu-Fe and Al-Pd-Mn alloys [8,[27][28][29]. During the past thirty years, several stable 2D and 1D quasicrystals and metastable 3D quasicrystals, as well as some quasicrystal approximants in the Al-Pd-Fe alloy, have been reported [5,[30][31][32][33][34][35]. For clarity, most known phases with their stoichiometry range in the ternary diagram of Al-Pd-Fe described by Balanetskyy et al are reproduced and shown in Figure 1 [34].…”

“…The structures of two other cubic approximants Al63.6Pd30.2Fe6.2 and Al68.9Pd17.1Fe13.9 with space groups Fm3 and Im3, respectively, have been found by single-crystal X-ray diffraction measurements [22]. However, the structure of Al68.9Pd17.1Fe13.9 (designated C1 phase, with a concise formula Al69Pd17Fe14) was updated with space group Im3 ̅ in another work [31]. Note that the Al concentration in the Al63.6Pd30.2Fe6.2 and Al68.9Pd17.1Fe13.9 phase is quite close to that of the Al39Pd21Fe2 and Al70Pd10Fe20 phase, respectively.…”