德国奥格斯堡大学Peter Lunkenheimer课题组在最新论文中研究了热膨胀和玻璃转变。2023年2月6日，国际知名学术期刊《自然—物理学》发表了这一成果。
该研究组发现，随着玻璃温度的升高，玻璃的热膨胀系数下降得更厉害，这标志着该材料类的液固交叉。
然而，当热膨胀系数与脆性（颗粒协同性的量度）成比例时，这种比例性又回来了。因此，要使玻璃变成液体，仅仅克服粒子间的结合能是不够的。相反，需要投入更多的能量来打破玻璃状材料中常见的典型协同粒子网络。液相的热膨胀系数也表现出类似的反常行为，并普遍增加了约3倍的常数因子。这些普遍性允许从热膨胀估计玻璃温度，反之亦然。
研究人员表示，根据林德曼判据，熔化可以描述为：当晶体材料的原子的热振动变得如此强烈，以至于它们摆脱了结合力而自行融化。这种情况并不一定适用于玻璃杯，在玻璃杯中，固液交叉的性质存在着激烈的争论。林德曼判据表明，晶体的热膨胀系数与其熔化温度成反比。
附：英文原文
Title: Thermal expansion and the glass transition
Author: Lunkenheimer, Peter, Loidl, Alois, Riechers, Birte, Zaccone, Alessio, Samwer, Konrad
Issue&Volume: 2023-02-06
Abstract: Melting is well understood in terms of the Lindemann criterion, which essentially states that crystalline materials melt when the thermal vibrations of their atoms become so vigorous that they shake themselves free of the binding forces. This picture does not necessarily have to hold for glasses, where the nature of the solid–liquid cross-over is highly debated. The Lindemann criterion implies that the thermal expansion coefficients of crystals are inversely proportional to their melting temperatures. Here we find that, in contrast, the thermal expansion coefficient of glasses decreases more strongly with increasing glass temperature, which marks the liquid–solid cross-over in this material class. However, this proportionality returns when the thermal expansion coefficient is scaled by the fragility, a measure of particle cooperativity. Therefore, for a glass to become liquid, it is not sufficient to simply overcome the interparticle binding energies. Instead, more energy must be invested to break up the typical cooperative particle network that is common to glassy materials. The thermal expansion coefficient of the liquid phase reveals similar anomalous behaviour and is universally enhanced by a constant factor of approximately 3. These universalities allow the estimation of glass temperatures from thermal expansion and vice versa.
DOI: 10.1038/s41567-022-01920-5
Source: https://www.nature.com/articles/s41567-022-01920-5