Title: Soft Mode Manifold Dynamics Behind Negative Thermal Expansion

Zach Schlesinger
Department of Physics
University of California, Santa Cruz This talk will include a summary of infrared and other measurements of a prototypical material, ZrW₂O₈, which exhibits a very large, isotropic contraction with increasing temperature. It will then focus on what simple models can tell us about why this happens. Of particular interest is an apparent deficit of strong short-range bonds, compared to conventional crystal structures, and the connection between this microscopic underconstraint and the macroscopic phenomenon of negative thermal expansion.