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04 April 2015 - Chemical Zoo

You would expect that by now chemists haver tackled all small molecules and have ventured on with the larger ones. This is far from the truth. Simple binary compounds continue to pose problems and large tracts of the small ternary compound landscape are still unknown to science. It is therefore a happy occasion to welcome into the expanding family of chemical compounds: ZrIrSb as reported by Gautier et al. (doi) They have been intelligently exploring a chemical space defined by a known series of binary AX compounds relevant as semiconductors such as ZnO expanded by cobalt, rhodium or iridium. Of the initial set of 483 potential compounds only 83 have ever been synthesised, for example LaNiSb or ZrPtSi so it was clear work was needed to be done.

Of the possible remaining 400 compounds the thermodynamic stability was calculated by DTF, basically the energy of the most likely crystal structure (together with phonon stability) compared to that of the constituents or any other compound configuration (unary, binary) from what can be understood from the article. 54 compounds survived this screening, the others are deemed incurably unstable. For example the hypothetical CaNiO exists more happily as a mixture of CaO and elementary nickel.

In the second phase several compounds were synthesised using arc melting and quartz-tube annealing and ZrIrSb was one of the new compounds found to form a single phase. Identification was based on XRD AND SAED. The crystal types were determined by TEM. Additional bonus for ZrIrSb, it is not only a conductor , it is also a transparent conductor.