Pressure is a fundamental thermodynamic variable that spans roughly 50 orders of magnitude throughout the universe, yet practically all of our chemical intuition is based upon results obtained near atmospheric conditions. At pressures on the order of millions of atmospheres—the kind found deep within our planet—elemental properties that we consider fundamental become categorically altered. For example, atomic volumes drop sharply, valence orbital energies can fall below those of core orbitals, and electronegativities drift from their tabulated ambient pressure values. Even at relatively modest pressures of ~10,000–100,000 atm, which are now readily accessible in the laboratory, these effects can lead to surprising new chemical bonding, structures, and properties, opening up a new frontier for chemical exploration. In this talk, I will show how we have harnessed pressure to: (i) exert thermodynamic control to synthesize novel binary bismuth intermetallic compounds that are impossible to synthesize using traditional methods; and (ii) determine chemically-pure structure–function correlations in jarosite, a magnetically-frustrated mineral.




James Walsh, PhD (Northwestern University)