Refinement of the Crystal Structures of Palladium-rich In-Pd Compounds by X-Ray and Neutron Powder Diffraction

Abstract

The ternary indium palladium intermetallics In 3 Pd 5 , InPd 2 , and InPd 3 have been synthesized by iodine-catalyzed reactions from the elements. Rietveld refinements on X-ray powder diffraction patterns provide the first accurate crystal structure data for (8) pm, Co 2 Si-type). X-Ray powder diffraction apparently confirms the TiAl 3 structure type proposed in the literature for InPd 3 . However, Rietveld refinement on neutron powder diffraction data reveals an In/Pd distributional disorder. Therefore, we describe the crystal structure of InPd 3 in a AuCu-type model instead (P4/mmm, No. 123, a = 287.224(4), c = 380.079(7) pm), with mixed occupancy of one crystallographic site by 50 % In and 50 % Pd. In contrast to In 3 Pd 5 and InPd 2 , which can be considered to be line compounds, InPd 3 shows a non-negligible homogeneity range with unit cell volumes ranging from 0.126132 (5)

Synthesis and crystal structure of a new Cu3Au-type ternary phase in the Au–In–Pd system: distribution of atoms over crystallographic positions

“…Examples of mixed occupancy of the same positions by In atoms together with atoms of noble metals (Au and Pd) in intermetallics are known in the literature (Dmytriv et al, 2011;Palasyuk & Maggard, 2010), though they are not frequent. This is also consistent with the character of the atomic distribution in the CuAu-type structure of the binary InPd 3 phase, where In also gives a mixed occupancy with Pd (Kohlmann & Ritter, 2007, 2009. Kohlmann & Ritter (2009) suggested that valence electronic concentration (VEC) is an important factor defining the structure type of intermetallics with a high Pd content.…”

“…Later, two further modifications of InPd 3 with the ZrAl 3 and TiAl 3 structure types were found (Bhan & Schubert, 1969). These results were confirmed and refined by Kohlmann & Ritter (2007, 2009, who used neutron diffraction, which does not suffer from the problem of the close X-ray scattering factors of Pd and In. In agreement with the suggestions of Schubert (1955), the atomic distribution in the CuAu-type modification of InPd 3 was found to be (Pd)(In 0.5 Pd 0.5 ).…”

Pd17In4Se4, a Metal‐Rich Palladium–Indium Selenide with an Open‐Framework Structure

“…Two ordered binary intermetallic compounds of a Pd 3 In composition have been previously reported,4 yet they do not adopt a strict Cu 3 Au‐type structure but rather that of its derivatives, TiAl 3 and ZrAl 3 . Also, a metastable (Pd 0.5 In 0.5 )Pd modification of the type CuAu was reported;5 it is, however, disordered and features mixed Pd/In occupancy, and thus falls out of our consideration. Both ordered intermetallic compounds share indium‐centered palladium cuboctahedra as the structural units and differ only in their packing.…”

Surface structures of In-Pd intermetallic compounds. II. A theoretical study

“…The stability against the demixion in pure Pd and InPd 3 has not been evaluated, since this compound contains some disorder. 41 The mixing enthalpy can then be expressed as a function of the dilute impurity enthalpy per In atom H imp…”