"Revealing Superconductivity by Density Functional Theory"

This event is sponsored by FAMU-FSU College of Engineering Department of Materials Science and Engineering.

Abstract: A coherent theory explaining superconductivity in both conventional and unconventional materials has been lacking. In this work, we propose that superconductivity originates from the formation of a symmetry-broken superconducting configuration (SCC) induced by atomic perturbations of the normal conducting configuration (NCC). This electron– phonon interaction generates straight one-dimensional tunnels (SODTs) for charge density, as revealed by density functional theory (DFT) calculations for both conventional and unconventional superconductors. These SODTs act as resistance-free superhighways and are correlated with Cooper pairs described in the Bardeen– Cooper–Schrieffer (BCS) theory, suggesting that BCS theory applies universally to all superconductors. In conventional superconductors, SODTs are embedded within the bulk matrix and are easily disrupted by matrix phonon vibrations, resulting in low critical temperatures as predicted by BCS theory. In contrast, in unconventional superconductors such as YBa₂Cu₃O₇ (YBCO7), SODTs are protected by a layered pontoon structure with weak bonding to the bulk matrix, preserving their integrity at higher temperatures and enabling much higher critical temperatures. This unified theory demonstrates that DFT can serve as a practical tool for predicting superconductivity, paving the way for systematic discovery of new superconducting materials.

Zi-Kui Liu, Ph.D., FASM, FTMS

Professor of Materials Science and Engineering

Pennsylvania State University

Speaker Bio: Zi-Kui Liu is the Professor of Materials Science and Engineering at The Pennsylvania State University. He earned his Ph.D. in Physical Metallurgy from the Royal Institute of Technology (KTH), Sweden, and holds degrees from Central South University and University of Science and Technology Beijing in China. Dr. Liu is internationally recognized for pioneering computational thermodynamics and materials design, including coining the term Materials Genome®. His research integrates first-principles calculations, machine learning, and thermodynamic modeling to accelerate materials discovery. He has published over 700 peer-reviewed papers and three patents, authored the book Computational Thermodynamics of Materials, and graduated more than 35 Ph.D. students. Dr. Liu has served as the President of ASM International, and recipient of numerous honors, including the ASM J. Willard Gibbs Phase Equilibria Award and the TMS William Hume-Rothery Award.