The Experimental Search for New Predicted Binary-alloy Structures

Predicting new ordered phases in metallic alloys is a productive line of inquiry because configurational ordering in an alloy can dramatically alter their useful material properties. One is able to infer the existence of an ordered phase in an alloy using first-principles calculated formation enthalpies.\footnote{G. L. W. Hart, ``Where are Nature's missing structures?'' Nature Materials 6 941-945 2007} Using this approach, we have been able to identify stable (i.e. lowest energy) orderings in a variety of binary Pt-based alloys, many of which have never before been observed experimentally. After preparing alloys of the desired composition, we performed synchrotron x-ray powder diffraction experiments to prove or disprove the expected orderings.