When the liquid is rapidly cooled or pressurized, it will avoid crystallization and change to an amorphous glass. Almost all condensed systems can form a glass state. Therefore, glass transition is a common physical phenomenon. However, as a representative of the amorphous liquid-solid transition, the glass transition cannot be simply categorized as a known type of phase transition, making its nature of phase transition a problem that has plagued condensed matter physics for many years. At the 125th anniversary of the publication of Science, Science raised 125 major scientific issues that need to be resolved urgently in this century, and "What is the essence of the glass state" is among them. Many theories have been proposed in history to try to explain the glass transition, but so far no theory can really solve the problem.
Professor Xu Ning's research group of the Key Laboratory of Soft Matter Chemistry, the National Laboratory of Microscale and the Department of Physics of the Chinese Academy of Sciences has been engaged in theoretical research on the nature of amorphous solids and amorphous liquid-solid transitions. Wang Lijin and Xu Ning The professor's research found that the glass transition temperature can be predicted by the structure and vibration characteristics of zero-temperature glass, thus making a new interpretation of the glass transition from a solid perspective. The research paper was published in the Physical Review Letters.
Liquid theory has an important approximation: although there is attraction between liquid molecules, the thermodynamic properties of the liquid are mainly determined by the repulsion between the molecules, and attraction is only perturbation. This approximation greatly simplifies the calculation of liquids and is an important milestone in the development of liquid theory. However, recent studies have found that in supercooled liquids that tend to glass transition, the attraction cannot be simply regarded as perturbation. How to understand this non-perturbation effect has therefore become a new challenge. Dr. Wang Lijin and Professor Xu Ning uniquely explained the non-perturbative effect of attraction in supercooled liquids from the perspective of zero-temperature glass: this non-perturbation effect is entirely derived from the corresponding system of attraction and pure repulsion Differences in the structure of zero-temperature glass. This structural difference makes the attractive glass have a higher characteristic vibration frequency and weaker low-frequency vibration mode localization than the pure repulsive glass, thus making the attractive glass more stable and has a higher glass Chemical transition temperature, the corresponding supercooled liquid dynamics will be significantly different. More importantly, starting from the structure and vibration characteristics of zero-temperature glass, Dr. Wang Lijin and Professor Xu Ning proposed an empirical expression of the glass transition temperature completely characterized by the structure and vibration physical quantity of zero-temperature glass. The results given are in good agreement with the results of computer simulation quantitatively. This study shows that the glass transition can be completely understood from the characteristics of solid glass, thus opening up a whole new way of thinking for the study of glass transition.
This research was supported by the Fund Committee, the Ministry of Science and Technology, the Chinese Academy of Sciences and the Ministry of Education.
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