InPd 3-x Cu x (x = 0-1) were prepared by high temperature synthesis starting from the highly pure constituent elements. The crystal structures were determined by X-ray diffraction. In the structure of InPd 3-x Cu x (x = 0-1), Cu stabilizes the TiAl 3 -type InPd 3 and selectively substitutes one of the two Pd positions and at the limiting composition ordered InPd 2 Cu is formed where Cu completely occupies that position. The intriguing selective substitution was investigated by first-principles total energy calculations followed by electronic structure and chemical bonding analysis.

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The ternary phase with the composition Ni 3 InSb has been synthesized by high-temperature synthesis and structurally characterized by a combination of X-ray analysis, neutron diffraction analysis, and theoretical calculations. The structure of Ni 3 InSb crystallizes in the orthorhombic space group Pnma with lattice constants a = 7.111(3) Å, b = 5.193(3) Å, and c = 8.2113(2) Å. The crystal structure contains ∼20 atoms in its unit cell, which are distributed over four crystallographically independent positions (two Ni, one In, and one Sb). The crystal structure can be considered as a ternary substitutional variant of Ni 3 Sn 2 (Pnma, no. 62), where a trivalent In and a pentavalent Sb orderly occupy two tetravalent Sn sites of Ni 3 Sn 2 . This site decoration pattern of two neighboring elements, In and Sb, is unique and confirmed by first principles total energy calculations. The crystal structure can be described by two building units: Ni 2 Sb (building unit of Ni 2 In) and NiIn (NiAs-type). They alternate in the crystal structure and form infinite acslabs (puckered), and the slabs are stacked along [010]. A triangular lattice formed by Ni atoms indicates the existence of a geometrically frustrated structure. The calculated density of states and crystal orbital Hamilton population enlighten the stability and bonding characteristics of the structure.The temperature-dependent neutron diffraction study down to 5 K reveals that the crystal structure remains in the same orthorhombic symmetry with a weak anomaly in the lattice parameters at ∼100 K. Detailed temperature-and magnetic field-dependent magnetic properties of the title phase Ni 3 InSb show spin-glass-or spin-disorder-like behaviors below ∼300 K with an unusual magnetic behavior below 100 K, where an enhancement of magnetization with a decrease of the coercive field has been found.

The unique site substitution of Zn in the structure of tetragonal Cu3Zn2Sb2 and the substitution of Cu in the binary InPd3, followed by the formation of Cu5Zn3Sb2 and InPd2Cu has been addressed from fundamental perspectives. First principles total energy calculations, and semi-empirical electronic structure calculations using both the density of states, crystal orbital Hamilton population, and Mulliken population analysis were performed to understand the observed compositional range for both the titled cases and to address the “coloring problem” for the experimentally observed site preferences.

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