Chlorine nuclear quadrupole resonance studies of K₂IrCl₆-K₂PtCl₆ solid solutions

Abstract

The cubic lattice parameters for the solid solution system K₂IrCl₆- K₂PtCl₆ vary approximately linearly with composition from a₀ = 9.765±0.001 Ǻ for K₂,IrCl₆, to a₀ = 9.748±0.001 Ǻ for K₂PtCl₆. The ³⁵Cl n.q.r, frequencies show shifts from the frequencies observed in the pure compounds, these shifts being approximately linear with composition at each of the temperatures 77°K, 201°K, and 298°K. The shifts in frequency on going from 0-100% Pt are, for the chlorine atoms bonded to the iridium, +93 kHz, and for the chlorine atoms bonded to the platinum, +84 kHz.     The infrared stretching frequencies of the MCl₆^2- groups also show shifts which are approximately linear with composition. The extrapolated shifts in going from 0-100% Pt are +11 cm^-1 and +4.5 cm^-1 for the Pt-Cl and Ir-Cl stretching frequencies, respectively. The n.q.r. and infrared results are best accounted for by small changes in the M-Cl bond lengths within the MCl₆^2- group, with concurrent changes in a₀, and possibly also in the positional parameter u. Re-examination of the variation of magnetic susceptibility with composition in the K₂IrCl₆-K₂PtCl₆ system is also reported, and reasons proposed for the form of this variation.     ³⁵Cl n.q.r. frequencies are reported for Cs₂IrCl₆.