Dr. Julia Medvedeva, professor of physics at S&T, contributed to a research paper recently published by the Journal of the American Chemical Society on novel phase-change material that exhibits polyamorphism — a transition between two distinct amorphous states. The article is titled “Multistates and Polyamorphism in Phase-Change K₂Sb₈Se₁₃” and is included in the journal’s 2018 issue.

Medvedeva collaborated with a group of experimentalists from Northwestern University to understand the microscopic origin of the transitions in a material named K₂Sb₈Se₁₃. Read the abstract.

Medvedeva performed atomistic computer simulations of the three phases of K₂Sb₈Se₁₃ and then calculated the resulting optical and electronic properties of the phases. Her results showed that the transitions in this material are driven by the atomic coordinative preferences of the Sb atoms, — or how many Se atoms surround the Sb atom. Because the Sb-Se interatomic interactions govern the electrical and optical properties in the material, changes in the number of selenium neighbors from 5 to 4 to 3 upon the transitions result in sharply contrasting electrical resistivity and optical transmission window at each transition.

Medvedeva says this three-state behavior holds promise for various new science experiments, including applications related to higher-than-binary types of computing logic circuits and reconfigurable logic devices.