When being quenched or compressed fast enough to avoid crystallization, a liquid can freeze into a glass. The glass transition has attracted general interests because almost all condensed matter can vitrify. However, the glass transition cannot yet be simply classified into any well-known types of phase transition. The nature of glasses therefore remains elusive and was also selected by Science on its 125th anniversary as one of the 125 important scientific problems to be resolved. A lot of theories have been developed to explain the glass transition, but none of them serves convincingly as the final solution.
The Theoretical and Computational Soft Condensed Matter Physics group led by Prof. XU Ning from CAS Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory for Physical Sciences at the Microscale, and Department of Physics have been focused on the study of the nature of amorphous solids and noncrystalline liquid-solid transition. Recently, Dr. Lijin Wang and Prof. Ning Xu found that the glass transition temperature could be predicted from the structural and vibrational properties of the zero-temperature glasses, which provides a novel understanding of the glass transition in the perspective of solid. The paper of this study has been published in Physical Review Letters on February 7, 2014 [Phys. Rev. Lett. 112, 055701 (2014)].
An important approximation in the theory of simple liquids is that thermodynamic properties of dense liquids are determined mainly by the repulsive part of the interaction, while the attraction acts as a perturbation. However, it has been shown in recent studies that in supercooled liquids approaching the glass transition the attraction cannot be simply treated as a perturbation. Dr. Lijin Wang and Prof. Ning Xu successfully explained the nonperturbative effects of attraction in supercooled liquids from the perspective of the zero-temperature glasses: The nonperturbative effects originate from the structural differences between the zero-temperature glasses with and without attraction. Such differences result in a higher characteristic frequency and weaker low-frequency quasilocalization of vibration for glasses with attraction than purely repulsive ones, which makes the glasses with attraction more stable with higher glass transition temperatures. Consequently, there are obvious dynamical differences between supercooled liquids with and without attraction. More importantly, they proposed an empirical expression of the glass transition temperature based on purely structural and vibrational quantities of the zero-temperature glasses, which agrees quantitatively well with the results from molecular dynamics simulation. Overall, this study reveals that the glass transition can be probed from properties of zero-temperature glasses and thus provides a new perspective on this long-standing problem.
This work was supported by the National Natural Science Foundation, Ministry of Science and Technology, Academy of Sciences, and Ministry of Education.
http://prl.aps.org/abstract/PRL/v112/i5/e055701
(Hefei National Laboratory for Physical Sciences at the Microscale, School of Physical Sciences)
