Entropy has been at the core of the thermodynamics of solids since the days of Gibbs. Gibbs had ideas about the statistical entropy of atomic configurations, but he did not know about phonons or electrons. It turns out that vibrational entropy plays a central role in many phase transitions in materials. This talk will explain how we use inelastic scattering of neutrons and photons to learn why crystal structures and local chemical environments alter the phonon density-of-states of materials. Effects of anharmonicity, microstructure, and electronic entropy may also be described.

ANL Physics Division Colloquium Schedule