Mapping the genome of intermetallic clathrates

Inorganic clathrates and, in general, semiconducting host/guest compounds feature unique properties, such as ultra-low thermal conductivity, high carrier mobility, superconductivity, and high-density ion storage. They consist of tetrahedrally coordinated frames of nanometer-size polyhedral cages encapsulating metallic guest atoms. Whereas conventional clathrates normally contain group 14 elements (Si, Ge, Sn) as framework atoms, a few stable intermetallic “unconventional” clathrates have been discovered and characterized.

In this work, we have developed a high-throughput approach that combines electronic structure theory and machine learning to systematically compute the formation energy of several thousand compositions and identify new stable ternary and quaternary compounds.

Several proposed compositions have been tested by synthesis providing feedback to the calculations and leading to the discovery of new intermetallic host/guest compounds with either clathrate-like or competing structures. Single-phase synthesis and first-principles calculations enabled the joint theoretical and experimental characterization of their transport properties, revealing promising thermoelectric performance, other-disorder phase transitions, and extremely low thermal conductivity.