Shanti Deemyad, an Associate Professor of Physics and Astronomy, recently helped solve a long-standing mystery about lithium, the first element in the periodic table that is metallic at ambient conditions. Lithium, which is a key element in electronics and battery technology, has played an important role in the development of modern condensed matter theories.
The crystal structure of materials at zero pressure and temperature is one of their most basic properties. Until now, it was thought that a complex arrangement of lithium atoms, observed during cooling in the laboratory, was its lowest energy state. But the idea baffled theoretical physicists since lithium has only three electrons and therefore should have a simple atomic structure.
Deemyad’s new study combined theory and experimentation to discover the true structure of lithium in its lowest energy state at cold temperatures.
Her research group prepared the lithium samples in tiny pressure cells at the U. The group then traveled to Argonne National Laboratory to apply pressure up to 10,000 times the Earth’s atmosphere – by pressing the samples between the tips of two diamonds – and examine the structures at low pressure and temperature using synchrotron X-ray beams.
The experiment proved that lithium atoms are in their lowest energy state when arranged in a simple structure, like oranges in a box. The study showed that the complex structure observed during cooling is only a metastable structure and the transition to this state is due to kinetic reasons or because it is a faster transition than one to its true ground state.
The study also provided what may be the first direct evidence of quantum solid behavior in a metal, an exciting observation that is related to another of Deemyad’s research interests, metallic hydrogen. The lithium results were published in the journal Science in June.
Deemyad’s research is currently supported by a National Science Foundation Career Award, which provides $620,000 over a five-year period.
Deemyad joined the faculty as an assistant professor of physics and astronomy in 2010. Her lab is divided in two major areas: quantum solids and highly correlated electron systems with an emphasis on studying the nature of electronic interactions; and high pressure guided synthesis of materials with new or enhanced properties for energy storage and transport.