(a) Ca14Au45Sn6 (b) CaAg3.5In1.9 (c) SrAu4.3In1.7

Hexagonal Au star

Honeycomb-like template

Disorder in tunnel

Gold-Rich Complex Intermetallic PhasesJohn D Corbett, Iowa State University, DMR 0853732

Electron-poor intermetallics represent a special class of phases that are electronically nearby the Hume-Rothery phases (including quasicrystal and approximants that we have extensively explored in both former and current projects) in terms of the valence electron counts per atom (e/a). The structures of and bonding in these phases are often very complex and exotic, thus they can offer chemists unique objects with useful and novel characteristics, especially those that impact the challenge of providing clean and secure energy via improved abilities and efficiencies in converting energy.

Au is a magic element not only because it has the largest relativistic effects among all elements; The introduction of Au as a dominant component in polar intermetallics ensures the formation of complex intermetallic phases that feature low e/a and novel bonding patterns such as in (a) Ca14Au45Sn6,1 (b) CaAg3.5In1.9, and (c) SrAu4.3In1.7.2 Individual atom characteristics seem very important. Thus, substitutions of Ag for Au (b) or Sr for Ca (c) into the quasicrystal/approximant phase region CaAu4In2 give these new structures instead.

1. Qisheng Lin, John D Corbett, Inorg. Chem., 2011, 50, 1808.2. Qisheng Lin, John D Corbett, Inorg. Chem., 2011, submitted.

Gold-Rich Complex Intermetallic PhasesJohn D Corbett, Iowa State University, DMR 0853732

World wide impacts:Development of new areas of chemistry that have been followed by world-wide growth and development has been long-term feature of this program. This has involved the discovery and application of new chemistry to diverse areas of solid state chemistry over multiple decades. Particular evolution has been seen in recent years for intermetallic and metal-rich systems. The valence, bonding, and structural concepts in traditional chemistry are of little use or applicability for intermetallics, lacking any general concepts of extended, delocalized bonding and applicable structural dictates. Still, intermetallic examples of very strong delocalized bonding and high coordination numbers can be found, generally in parts of the periodic table that are very little known, studied, or understood. A modest international community has developed along these lines, including former group members on chemistry faculties around the world. It is significant that special topical issues on “intermetallics’’ are presently in the editing/printing stages for two international journals, European Journal of Inorganic Chemistry and Z. Anorg. Allg. Chem. (Journal of Inorganic and General Chemistry). Our NSF effort has particularly led the way in the search for new quasicrystals and their crystalline approximants and also for what may be termed “inverse Zintl phases”, polycationic clusters of rare-earth-metals strongly stabilized by interstitial atoms with simple monoanions.