Takeshi Egami

Dr. Takeshi Egami is UT-ORNL Distinguished Scientist/Professor of the University of Tennessee at Knoxville, with join appointment at the Oak Ridge National Laboratory. He received his B. E. degree in applied physics from the University of Tokyo in 1968, and his Ph.D. in materials science from the University of Pennsylvania in 1971. After the postdoctoral research at the University of Sussex in U.K. and Max-Planck-Institut in Stuttgart, Germany, he returned to the Department of Materials Science and Engineering of the University of Pennsylvania as a faculty in 1973 (Dept. Chair 1997-2002) until he moved to the current position in 2003. He was Founding Director of UT-ORNL Joint Institute for Neutron Sciences (2008-2015). He received B. E. Warren Award for Diffraction Physics from ACA in 2003 and other awards. He is Fellow of the APS, NSSA and AAAS. Dr. Egami has published 1 book, 35 reviews and over 580 papers.

Abstract Title: Bright Side of Disorder

Abstract:

The word “disorder” has a negative connotation; social disorder, mental disorder, etc. But it has a bright side, as an agent to allow freedom of choice and creativity out of norm. In condensed matter, disorder can trigger emergent phenomena by breaking the lattice symmetry. It is best characterized and quantified by scattering measurements of neutron and X-rays. They provide direct access to the static and dynamic correlation functions which help define the degree of local order. The method of pair-distribution function (PDF) has long been used to describe the structure of glasses and liquids. It is obtained by Fourier transforming (FT) the total structure function S(Q), measured by diffraction. Even though it has a long history, it has suffered from low reputation because of the FT errors known as termination errors, which occur when the range of Q measured is not wide enough. However, the advent of synchrotron-based sources drastically diminished this problem. Recently the approach has been extended to describe dynamics, through the energy-resolved dynamic PDF, g(r, E), and the Van Hove function, G(r, t), obtained by the FT of the dynamic structure factor, S(Q, ). It is applied even to the observation of dynamic correlation among electrons using inelastic X-ray scattering. “Disorder” is a negative word. In real world nothing is truly disordered, and particles are statically or dynamically correlated. Recent advances in instrumentation for scattering now allow us to catch these correlations and elucidate the properties of seemingly disordered matter.