Physics Colloquium: Exploring Energy Dissipation in Ni-based Concentrated Alloys
Prof. Sai Mu, University of South Carolina
Abstract: Disordered alloys are essential to modern technologies, from energy and transportation to construction, communication, and medicine. Recently, High Entropy Alloys (HEAs) and multicomponent Concentrated Solid Solution Alloys (CSAs) have gained numerous attentions for their exceptional physical properties. This talk examines how chemical complexity influences the electronic and vibrational behaviors of such alloys, with a focus on Ni-based concentrated solid solution alloys. In the first part, we explore the effects of disorder on electrical resistivity using ab initio electronic structure methods, identifying and analyzing the dominant electron scattering mechanisms in these highly disordered alloys. In the second part, we investigate the role of force constant disorder on lattice vibrations and phonon scattering in CSAs. Our findings reveal the previously unrecognized influence of local chemical environments on the force constants of atomic pairs, significantly affecting phonon scattering. These discoveries have broad implications for alloy design, offering pathways to develop materials with tailored properties—such as improved energy dissipation, phase stability, and enhanced mechanical performance—through the strategic use of extreme compositional complexity.
BIO: Sai Mu received his PhD in condensed matter physics from the University of Nebraska-Lincoln in 2014, focusing on the first principles study of magnetoelectric antiferromagnets for spintronic applications. Following this, he started his postdoctoral research at Oak Ridge National Laboratory, exploring the energy dissipations through electron and lattice degrees of freedom in extremely disordered high entropy alloys. Transitioning to the University of California, Santa Barbara from 2019 to 2022, he studied defect physic of wide bandgap materials, addressing their electrical and optical properties. Now he is an assistant professor at the University of South Carolina, where his research focuses on quantum defects in semiconductors and the emergent phenomena in magnetic quantum materials.