Pennsylvania State University

报告人简介：

　　Long-Qing Chen is Donald W. Hamer Professor of Materials Science and Engineering, Professor of Engineering Science and Mechanics, and Professor of Mathematics at Penn State. He received his Ph.D. from MIT in Materials Science and Engineering in 1990 and joined the faculty at Penn State in 1992. He has published over 500 papers in the area of computational microstructure evolution and multiscale modeling of structural metallic alloys, functional oxide thin films, and energy materials. For his research accomplishments, he has received numerous awards including the 2014 MRS Materials Theory Award, a Guggenheim Fellowship in 2005, the Humboldt Research Prize in 2017, and the 2011 TMS EMPMD Distinguished Scientist Award. He is a Fellow and Life Member of The Minerals, Metals and Materials Society (TMS) and a Fellow of the Materials Research Society (MRS), American Physical Society (APS), American Ceramic Society (ACerS), and ASM International (ASM). He is the Editor-in-Chief for npj Computational Materials by Nature Research.

报告摘要:

　　This presentation will discuss the applications of the phase-field method to understanding and discovering new mesoscale polar states that might emerge from nanoscale ferroelectric heterostructures subject to different mechanical and electric boundary conditions. As an example, the determination of thermodynamic conditions and geometric length scales leading to the formation of ordered polar vortex lattice as well as mixed states of regular domains and vortices in ferroelectric superlattices of PbTiO3/SrTiO3 using phase-field simulations and analytical theory will be presented. Switching of these vortex lattice states might produce other transient polar states such as polar skyrmions. It is shown that the stability of these vortex lattices involves an intimate competition between long-range electrostatic, long-range elastic, and short-range polarization gradient-related interactions leading to both an upper- and a lower- bound to the length scale at which these states can be observed. We further predicted the periodicity phase diagrams that show excellent agreements with experimental observations by collaborators.

邀 请 人：翁红明（电话：82649941）

联 系 人：李园园（电话：82649364）