On the morning of August 31, 2024, the "Freshman Education - Frontiers of Professional Development" lecture, organized by the School of Materials Science and Engineering at Tsinghua University, was successfully held in Room C217 of the Yifu Technological Science Building. Senior Professor GU, Lin delivered a special lecture titled as "The Origins of Functionalities in Functional Materials", over 100 new graduate students of class 2024 attended the lecture.

Lin delivering the freshman lecture on "The Origins of Functionalities in Functional Materials."

Lin started with the essence of batteries and, combining his group's latest work, analyzed the importance of vacancies, defects, and phase design in enhancing battery energy density. He infered the macroscopic changes in battery performance from microscopic aspects such as electronic scale, leading to a framework for the quantification of materials science. Lin pointed out that reductionist materials science heavily relies on our understanding of elements, progressing from completely solvable atomic energy levels to phase energy bands solvable under specific boundary conditions, and ultimately to macroscopic material properties that may only have statistical solutions.

Lin comprehensivly introduced how electronic structures at the atomic scale can affect the material properties. He began with the essence of ferroelectricity—specifically, the breaking of center inversion symmetry—and used d0-type ferroelectric structures as an example to discuss the correlation between the superior ferroelectric and piezoelectric properties of elements like Pb and Bi and the collapse of their outermost 6s electrons. He attributed the functionality of functional materials to local symmetry and fields, emphasizing that local symmetry can be modulated through the four fundamental degrees of freedom: lattice, charge, orbital, and spin. This modulation, in turn, allows for the exploration of the fine structure and novel functionalities of materials.

Lin explaining the microscopic principles of Pb and Bi ferroelectric materials

Subsequently, based on the findings from top international research, Lin analyzed the relationship between the performance of energy storage materials and microscopic degrees of freedom. He highlighted the importance of electron microscopy characterization in studies related to topologically protected electronic channels, defects in high-entropy alloys, the folding of d-band center planes, and new mechanisms of ferroelectric phase transitions. Finally, Lin emphasized the reversibility of condensed matter cognition, using a comparison between the twelve-tone equal temperament and the pentatonic scale to encourage students to think about how to explore a complete set of "basis" functions to describe the structure-function relationships of materials in the three-dimensional real space atomic coordinates.

Students attentively listening to Lin's lecture

During the discussion session, Lin addressed the new students' concerns regarding scientific research and career development. He emphasized that groundbreaking research requires a solid foundation in physics and a long-term research plan. He suggested that while students doing their own research, they should also gain inspirations by focusing on the state of art development of their research fields. Additionally, Professor Gu encouraged students to engage in collaboration, allowing sparks of wisdom to emerge from interdisciplinary exchanges.

The student representative presenting flowers to Lin

In this lecture, Professor Lin Gu not only provided insights into the research background and cutting-edge developments in electron microscopy but also shared his experiences on the path of scientific research. Through his discussion on the origins of functionality in functional materials, he inspired new students to reflect on materials science research. In response to questions from students about their professional fields and personal development, Professor Gu offered detailed answers. He encouraged students to clarify their research interests, engage in fundamental research, and actively communicate with their peers for mutual progress.

Introduction:

GU Lin, a professor and doctoral advisor at the School of Materials Science and Engineering, Tsinghua University, has received the National Science Fund for Distinguished Young Scholars and the Special Award for the 16th China Youth Science and Technology Award. He leads key frontier exploration projects funded by the National Natural Science Foundation of China and major projects under the National Key Research and Development Program. His long-term research focuses on electron microscopy, using lattice, charge, and orbital degrees of freedom to reveal the atomic and electronic structures of functional oxides and energy storage catalytic materials. He achieved direct observation of the electron occupancy states of orbital degrees of freedom. Professor Gu has published over 900 SCI papers (including 19 in Nature and Science, and over 120 in their sub-journals), with more than 100,000 citations and an h-index exceeding 170. He has been listed multiple times as a Clarivate Highly Cited Researcher globally.